Protect Thy Enemy

Desires & Duties Duet #1

by Marilyn Don

For lovers of Ana Huang’s Twisted Games and Catherine Cowles’ Hidden Waters, this slow-burn romance crackles with tension and suspense.

Arden Williams has spent her whole life proving she belongs. First at the academy, now as a rookie agent in the Secret Service. But when she's assigned to Holden Grant, the cold and ruthless agent known for breaking recruits, she realizes her biggest challenge isn't the job--it's surviving him.

Holden Grant doesn't do distractions. Especially not ones with sharp eyes and sharper tongues. He's there to train her, not get tangled in the past she doesn't even know she's carrying. But Arden is a walking reminder of the ghosts he can't escape and the promise he never should have made.

Tension turns to fire. Fire turns to something neither of them are ready for.

Because in a world where loyalty is everything, falling for the enemy is the most dangerous move of all.

Packed with enemies-to-lovers tension, forced proximity, and forbidden romance, Protect Thy Enemy is a heart-racing start to the Desire & Duties Duet.

Genres: Dark Romance, Enemies To Lovers, Romance, Romantic Suspense, Mystery, Slow Burn, Contemporary Romance

270 pages, Kindle Edition

Published April 16, 2025

About the author

Marilyn Don writes romance for the daydreamers and trope-lovers who crave a little chaos with their love stories. When she's not writing, she's either working her 9 to 5, trying to finish her own degree, or chasing her four-going-on-forty-year-old around Atlanta. She enjoys reading way past midnight, watching an emotional anime, and rewatching her favorite comfort shows.

Reviews

[Bee · Rating 4 out of 5]

I could NOT STOP READING!!! It was such a page turner and my goodness the SLOW BURN!!!! I enjoyed it thoroughly and the reason I didn’t give it 5 stars is because I needed it to be longer! 😭 I would have loved for some of these scenes to be fleshed out a bit more but overall, I’d recommend this book if you’re looking for something to giggle and kick your feet over! I need the second book right now!

[Victoria Franklin · Rating 4 out of 5]

Marilyn Don you are sneaky! I loved this book! Such a fun unique plot that kept my attention the whole time. I flew through this book and had a hard time putting it down!

Arden a rookie fresh out of school to become a secret service agent. She got a job and now she must go through training to see if she gets to stay on as a new hire. She feels like she has everything to prove.

Holden a secret service agent that now trains new rookies. He is haunted from an accident that happened on the job. His friend and idol Leo died on the job and he still loses sleep over it. He is given a few new rookies which just so happen to be Leo’s daughter (Arden). He doesn’t want to work with her but has no choice.

This is a slooooowww burn but the sexual tension made it worth the wait. 🤪 There are so many secrets to unfold! I didn’t see the twists coming!

If you like romance suspense this one was so fun! Almost gives miss congeniality vibes but secret service!

“You’re playing with fire, Rookie.”

“Good thing I love the burn.”

This is dangerous. This is wrong. And I’ve never wanted anything more.

⭐️⭐️⭐️⭐️
🌶️🌶️

[Gina Burney · Rating 2 out of 5]

This book just wasn’t what I expected. At just over 250 pages, I usually fly through something this length in a single sitting—but this one took me 12 days to finish. I struggled to stay engaged, often stopping after just a chapter or two.

The biggest issue for me was the pacing. The story felt repetitive and overly drawn out, making it hard to stay invested in the characters or plot. While the book does end on a cliffhanger that could pique interest for the next installment, I’m not sure I’m willing to go through another slow and repetitive ride to get those answers.

If you're looking for a fast-paced, tightly written enemies-to-lovers or suspense-filled romance, this might not be the one. It had potential, but ultimately it just didn’t deliver what I was hoping for.

[Loves2 Read · Rating 4 out of 5]

I received this book as an ARC, however all my thoughts are my own.

First of all…Marilyn, how DARE you leave me hanging like that?! Seriously! 😩 Let me just say, I hate cliffhangers, especially when I feel like I'm finally getting to that point I've been waiting for... and this book did exactly that. So, on one hand, great job, Marilyn, for making me want to throw my Kindle across the room! But on the other hand... HOW. DARE. YOU! 😠

Listen up, because this is important: this is NOT your typical dark romance. Let that sink in. Now, with that important distinction made, let's talk about "Protect Thy Enemy." Arden Williams, fresh out of the academy and bursting with a desire to prove herself with the Secret Service, is a character you can't help but root for. Her drive and unwavering belief that she was born for this job are absolutely infectious. That is, until Agent Holden Grant steps onto the scene – the very man she's assigned to report to. Holden is undeniably exceptional at his job, but Arden throws him for a loop in ways you might not anticipate. He's carrying a weight of secrets, heavy ones that have the potential to either forge an unbreakable bond with Arden or shatter any possibility of connection. The central question of whether they can navigate their individual battles and the ghosts of their past to find a way forward together is utterly compelling.

I genuinely enjoyed "Protect Thy Enemy." When Marilyn labeled this a slow burn, she wasn't kidding around! Seriously, if you're expecting immediate darkness or instant gratification, you've come to the wrong place. Every chapter had me thinking, "Okay, this has to be the moment," and it kept me absolutely glued to the pages despite the deliberately unhurried pace. The suspense was definitely there, and honestly, there were moments that genuinely had my heart racing! As a huge fan of dual POV, I really appreciated the author's writing style, allowing us to delve into both Arden and Holden's minds. There were a few instances where I longed for a bit more detail within certain chapters, as some scenes felt like they jumped forward in time without sufficient connective tissue, leaving me wanting a smoother transition. But let's talk about the spice! 🔥 Oh boy, was the slow build worth the explosive payoff! The intensity was fantastic, and now I'm desperately craving more – I NEED to see where their story goes next! The character development was excellent; we truly got to know Arden and Holden, which made investing in their journey so much easier. The tension and heat between them are undeniably present, a true, simmering slow burn that gradually intensifies rather than igniting instantly, but it's incredibly intriguing. I am absolutely counting down the days until the next installment!

[Rachelle Carter · Rating 4 out of 5]

⭐️ARC Review⭐️
Spoiler Free!‼️
So this wasn’t my usual genre of dark romance, I don’t read a lot of agency/cop romances so this was a new take for me. I enjoyed this book and I am really looking forward to the next one.
Marilyn writes so well and it so easy to read and build the scenarios and situations in your head.
Holden Grant is Secret Service Agent set to train new recruits so when his late partners daughter walks through the doors and he’s told by his boss she’s his responsibility, the past comes crashing back but it just that he is pulled and drawn to her even though he shouldn’t be.
Arden Williams is dead set on making it, being the best and proving she has earned her place in the Secret Service but her new training Agent seems dead set on pulling her down and pushing every button she has and yet she can’t stay away from him no matter how hard she tries.
This book is full of angst and it is 100% slooooow burn. Part one of the duet leaves you reeling and wanting so many answers that even the reader feels is right in front of us but we just can’t quite make it all fit.
Marilyn threw in all the tropes a dark romance hinges on; touch her and die, forced proximity, Alpha Male, enemies to lovers and slow burn. She wrote Arden and Holden and all the supporting characters so well, giving each of them their own voice and flushing the story out wonderfully. Oh Luna and Agent Park? These two have me 🤔.

Be prepared that this is book 1 of 2 so this story does leave you wanting but definitely worth the ride.😍
Overall Rating:⭐️⭐️⭐️⭐️
Spice:🌶️🌶️.5

[Bethany Kahl · Rating 3 out of 5]

ARC REVIEW ✨ Protect Thy Enemy by Marilyn Don

First of all…Marilyn how dare you leave me with such a cliffhanger!?!

Now that that’s been addressed…

Arden Williams is fresh out of the academy and lands a job with the Secret Service. She’s excited and wants nothing more than to prove that she can do this. She was MADE for this. That is, until she meets Agent Holden Grant. The man she’s been assigned to report to. Holden Grant is damn good at his job but when it comes to Arden, he gets distracted. And not for all the reasons you’d think. Holden has secrets. Secrets that may make or break his relationship with Arden. Can Arden and Holden survive each other and the ghosts of their past? Or will they let the ghosts consume them and distract them from reality?

I really enjoyed Protect Thy Enemy. When the author said slow burn, SHE MEANT IT. Every chapter I’d say to myself “ok it’s going to be this chapter, any minute now” and it kept me wanting to read more! It was suspenseful and honestly a little thrilling! I enjoy when a book is in dual POV so I really liked the authors writing style. There were some times where I wish there was more detail in a chapter because it felt like the scene would go from one day to immediately doing something else that didn’t necessarily connect so I just wanted a little more filler. The spice!? Oh was it worth the wait 🥵 I really hope we get more because I NEED more of it.

Overall
3.5/5 ⭐️
1 🌶️

[Maz · Rating 4 out of 5]

⭐⭐⭐⭐
🌶️

Book 1 of the duet and does end on a cliff hanger. New author for me so wasn't sure what to expect but I did like the blurb.
For me I felt it started a bit slow but as the story progressed it got more interesting with all the secrets, tension and the enemy vibe between both MCs.
Arden was top in her class and she wants to train for secret service. I did feel for her as in a male dominate world, she has to work extra hard to prove herself. She was strong, sarcastic and so serious.
Holden is the man that is in charge of her and her training. He is the best at his job but he is also very broken after losing his mentor. That said mentor is Arden's dad that she never knew. Things from that night doesn't make sense and he can't seem to let go.
Holden doesn't want to be near her, not just because it is a reminder of her father, he is feeling things he shouldn't. He is very grumpy and very stern.
Now u dercover as husband and wife, which is making things even more difficult. It was a very very slow burn and we only get 1 Spicy scene and that's at 80%. I think a few more scenes would have been great. They had a lot of chemistry throughout the story.
That twist at the end, was definitely not expected and now I want to know what is going on???!!!! Plenty of twist, secrets, banter and chemistry.

[Nicole၄၃ · Rating 4 out of 5]

❤️‍🔥ARC Review❤️‍🔥
Protect Thy Enemy by Marilyn Don is amazing.

I loved the work place romance, the slow burn, enemies to lovers, touch her and die and the age gap tropes. The author nailed each and every one!
Working in the Secret Service working for the president and first family is something I wasn’t prepared to love but the action was so much fun. The slow burn created anticipation I was waiting and waiting for! And the cliffhanger!!!!

Plot: Arden Williams has spent her whole life proving she belongs. First at the academy, now as a rookie agent in the Secret Service. But when she's assigned to Holden Grant, the cold and ruthless agent known for breaking recruits, she realizes her biggest challenge isn't the job--it's surviving him.
Holden Grant doesn't do distractions. Especially not ones with sharp eyes and sharper tongues. He's there to train her, not get tangled in the past she doesn't even know she's carrying. But Arden is a walking reminder of the ghosts he can't escape and the promise he never should have made.
Tension turns to fire. Fire turns to something neither of them are ready for.
Because in a world where loyalty is everything, falling for the enemy is the most dangerous move of all.

A fantastic read!

[Brendee Vee · Rating 4 out of 5]

Nicely done! I didn’t expect to like this story as much as I did due to not being the typical type of story I read, but I was pleasantly surprised by it! The slow burn fire was scorching my finger as I turned pages! We meet Arden who is a newbie agent with the Secret Service, but she is also the face Holden didn’t expect! Holden is the veteran who does the rookies training and the twist of that story and the hidden hurt is real! No way did I expect it but it all made me want to be in my feelings, and be mom proud of Arden and protect her all at once!
The cliffhanger??? Ma’am I’m gonna need some answers pronto!! I love, love, love multiple POVs because I need to know what everyone is thinking (yes! I’m that type of reader!) but that also gets me to buy into the overall story more!

Great story and need the next in the series please and thank you!

Thank you to the author and Greys Promotion as how I received this as an ARC, but this is my honest review.

[Samantha Bosnick · Rating 5 out of 5]

I really enjoyed reading this book. the level of tension and heat kept me reading. The character building was very well done we were able to get to know them which is very nice. the tension and heat between the characters is hot, not putting the book down hot, but a slow burn.

Arden Williams has always felt like she is proving herself to others. She has become a secret service agent, a big accomplishment and she has been assigned to Holden Grant a cold ruthless not into always following the rules secret service agent. He is there to train her, which he isn't happy about because he knows her from the past. His friend Leo who died on the job which still haunts Holden is Arden's father. He made a promise that he regrets ever making.


A awesome read and not gonna give any spoilers so I am ending here...Oh a cliffhanger. oh my!!!!

[Joyffree]

WHAT!!
How can you leave me hanging like this?
I have been taunt with anticipation for most of this read
When she says slow burn, she means it
But these two were oh-so worth the wait

Such EXPLOSIVE Chemistry between these two
The back-and-forth banter
Their verbal knock-down, drag-out altercations
I admit there were many, many times I wanted to "educate" Holden, but Arden held her own most of the time
Our dear sweet Arden. Who never backs down.
Even when stepping back for a moment might be the better plan of action

This was truly a unique read.
The storyline was so different from the norm.
The characters' backstories gave so much support to the overall events
The challenges they each faced - both individually and as a team
There were scenes I would have enjoyed with a bit more detail. I have questions.
Overall, though, I am excited to see how this plays out

[AmyzBookNook · Rating 4 out of 5]

Protect Thy Enemy (Desires & Duties Duet, #1) is a flirty, slow-burn romance with suspense and tension. This thrilling dark romance is centered around Arden Williams who is a rookie secret service agent who is assigned to work with Holden Grant. Neither of them is thrilled about the partnership. However, Holden made a promise to his late friend Leo, who is also Arden’s father. As the story unfolds, the pent-up tension and feelings between them begin to intensify, making it inevitable and exciting. I’ve never read a Secret Service romance before, and I really enjoyed this one! I also love the book cover so much; it's beautiful.

𝐓𝐫𝐨𝐩𝐞𝐬:
Forced Proximity
Slow-burn
Romantic suspense
Enemies to lovers
Touch her and die

Thank you to Grey's Promotion and Marilyn Don for E-Arc copy.

[Hannah · Rating 3 out of 5]

Mixed emotions

✨chaotic reveiw✨

WHAT THE HECK WAS THAT!!!! UGH. I was just really getting into the book and BAM cliffhanger.

It took me a while to get into the book. In the beginning you are hit with a lot of charcters and I was confused for a bit.

I am ready for the next book that is for sure.

If you don’t like cliffhangers I would not read this book until the next book comes out. I don’t even know when the next book will be out! Nothing about the next book is at the end of the book I received.

It is a slow burn. That when everything came to a head it was 🥵.

For me, this was one of those books I had to pay attention too because there is so much going on. I want to get lost in a book not to have to remember much.

Will I read the next book? Yes, hopefully there is a refresher at the beginning of the book since there is so much in the book.

[Dymon Knapps · Rating 4 out of 5]

Protect Thy Enemy
Author: Marilyn Don
Rating:4/5⭐️⭐️⭐️⭐️
Spice: 🌶️🌶️

“This is your chance “. he says taking a step closer his gaze locked onto mine. “Because tonight there’s No mission. No cover. No rules. Just you and me. Fake husband and wife. And I’m about to show you exactly what it feels like to be mine.”


This was a fun read! Arden is badass
FMC and she knows it. Grant is ruthless and cold but I loved seeing him break for Arden. I usually don’t enjoy slow burns but this one I didn’t mind. Also love that this is an interracial enemies-to-lovers pairing. I am so glad that this left on a cliffhanger and there are a lot of ways this could play out. I hope to get more background on the characters and see what chemistry they have besides sexual tension.

[Lyndsay Blackman · Rating 5 out of 5]

Wow Marilyn Don you did it with this one, and the cliffhanger at the end, how could you!? No no but in all seriousness it was the best way to end it because you left me waiting and wanting more, so much more!

Leo leaves behind his daughter Arden and asks his best friend Holden to keep an eye on her not knowing exactly how far that promise would actually go!

Holden you showed restraint and tried your hardest to keep Arden at arms length, but well you know what they say love always win.

Arden you strong woman you left with unanswered questions that you hope to seek out and get answers to, only to be left with more questions at the end.

I can not recommend this book enough and now I’m just patiently waiting for all the unanswered questions.

[Wendy Livingstone · Rating 5 out of 5]

This is the first part of a duet, and this is Arden and Holden’s story.
Arden is a rookie agent for the Secret Service, and she is assigned to Holden, who is cold and ruthless, and renowned for breaking recruits.
After that doozy of a cliffhanger, I cannot wait to read the second part!
This is a well written action-packed story, which is a slow burn, with angst, secrets, suspense, intrigue, challenges, enemies / lovers, touch her and die vibes, forced proximity, and tension, which leads to an entertaining, and unpredictable dark romance.
I look forward to reading more from this author whose work I recommend.

[Nahi · Rating 4 out of 5]

Oh my gosh, this book had me totally hooked from the very first page! Protect Thy Enemy is just what I love in a romantic suspense, gripping tension, slow-burn chemistry, and emotionally charged characters.

Arden is fierce and determined, trying to make it big in the Secret Service. Holden is her cold, ruthless trainer with a past he can’t escape. Their relationship? It’s like fireworks! Their connection? It’s undeniable. And the secrets that tie them together? They’re game-changers!

Marilyn Don writes a story that’s just right. Not too fast, not too slow, with a cliffhanger that’ll have you reaching for the next book the second it’s out.

[Naughty Nightie · Rating 4 out of 5]

Arden is a rookie Secret Service agent and is sent on a mission with Holden. Holden is a man who promised her father he would protect her if anything happened to him. Marilyn keeps you turning the pages with all the mystery, intrigue, twists, and turns throughout the book. Holden and Arden feel an attraction towards each other, but it is against company rules for officers to have relationships.
I received an ARC for my voluntary and honest review for NN Book Blog. If you love a secret service mystery with an age-gap romance thrown in, then you'll enjoy this book. Be warned that this book ends on a big plot twist; I'm eager to read the next book to see what happens next.

[Arnela · Rating 5 out of 5]

ARC REVIEW: WHAT THE ACTUAL FUCKKKKK!!! this book literally left my jaw on the floor!!! First off, I want to say I absolutely devoured this book! Arden is such a badass FMC that doesn’t let the male dominated workplace get to her and Holden Grant is ruthless and cold af, I loved the tension, how slowly and deliciously Grant breaks for Arden. That slow burn had me screaming 😱 do it already!!! That when it started actually burning I felt it too🥵🥵🥵, on top of the heat, comes a cool story line of secret agents that I haven’t read before! It was intriguing, but the ending literally no words! What a cliff hanger. I know this just came out butttttt. WHENS THE NEXT BOOK!!?!?!?

[Manasa HR · Rating 5 out of 5]

I kept on reading and reading, did not even realize that i had already reached the end. Omg!, Ms. Marilyn you just had me scrambling and frustrated that book is over! How could you stop it there? I demand the next book immediately!
The plot revolves around simulations and missions of secret service agents. Arden the rookie is assigned to Holden the prodigy! Arden is headstrong and wants to prove she is here to stay and Holden is having a hard time keeping his composure around her.
Story is filled with Slow burn, angst, secrets, tensions, plot twists. Basically, everything that can get you hooked in!
Love it. I highly recommend this book for all!

[Torianna · Rating 4 out of 5]

I truly enjoyed reading Protect Thy Enemy. It took me until about 40% of the way through to really get into the story, however once I hit this point, I did not want to put it down. Arden and Holden are both complex in their own rights. Both having pasts to heal from with no clear path on how to navigate to the other side. Hate is at the forefront of their relationship as they do not know how to handle the emotions and feelings they have for each other. All the tension and secrets lead up to a shocking ending that will have you needing the rest of the story immediately.

[Rebecca · Rating 4 out of 5]

Excuse meeeee, that ending!! This was a tension filled, slow burning story with twists, turns, secrets, and an ending that I didn't see coming. Holden Grant is an alpha male secret service agent who is forced to train a new recruit, Arden Williams. As secrets and lies are uncovered, Arden realizes that she's been tied to Holden in ways she never expected, and in high stakes situations Holden & Arden can't deny the chemistry brewing between them.

Tropes:
Romantic Suspense
Enemies to lovers
Touch her and die
Slow burn
Cliffhanger
Hidden secrets
Spice 1/5

[Dara Wasalino Tremblay · Rating 4 out of 5]

Protect Thy Enemy is an interesting romantic suspense novel that interweaves tension and romance. It got off to a slow start, but once the plot kicked in the story flew by! FMC Arden is a rookie Secret Service Agent and MMC Holden is a veteran agent and Arden’s training officer. Initially things are rough because both characters are strong willed, but eventually their relationship deepens and the strength of their connection surprises both characters.

This book is the first book of a duet and the cliffhanger leaves you hanging for book two!

[Rebecca Billman · Rating 4 out of 5]

Arden is the new rookie in the Secret Service and she knows what it takes to prove she is meant to be there. Holden is her superior who loves to traumatize the new rookies.

They are always at each other's throats and their banter begins to stoke a fire that is starting to burn between the two of them.

Arden and Holden have a different kind of love that shines through and makes you really love their story!

I cannot wait to see what Marilyn has in store for the rest of this new series!

[Linda · Rating 5 out of 5]

WOW!
Cliff-hanger warning!

This new author has me tongue tied!
So much tension.
So many secrets.

And Holden, seasoned professional has been a part of Arden's life but why?

So many strings yet to be pulled!
I am definitely intrigued, and I was hard-pressed to put this story down!

Now, the dreaded wait for the next book!
I need to know!
I expect you'll be chomping at the bit for book two too!

[K Webz · Rating 4 out of 5]

Protecting Thy Enemy is well written in a way it leaves you wanting the answers to questions where it is right in front of you but you can’t put it together.

The characters of Holden and Arden are well written and the tension between them leads to the perfect slow burn. Holden has the protective energy and Arden has a strong personality, these two clash but they share a past that could be a distraction neither of them can afford.

[Tammy · Rating 5 out of 5]

This is my first read from this author and I already can't wait for more. Holden and Arden have this crazy intense chemistry, like off the charts felt thru the pages. Even though they shouldnt engage as he's her superior and they are on a mission that seems to get more complicated than they first thought. Both seem to have strings from the past that won't let them fully go. I can't not wait for more!

[Abigail McKinney · Rating 4 out of 5]

3.5 stars

This was an exciting fast paced but also slow burn that ended on a cliffhanger that left me wanting more! Holden and Arden have some serious slow burn chemistry but there is also a lot of secrets/hidden identity/mystery stuff happening. I love a capable FMC and Arden delivers on being a badass without sacrificing vulnerability. This was a great quick read and I will definitely be checking out the sequel!

[Kayla HB · Rating 4 out of 5]

Marilyn Don really knocked this one outta the park!
I was on the edge of my seat the entire time. Ending in a cliffhanger has me anxious for book two!

So this follows Arden and Holden who are both in the Secret Service. Holden is her trainer and has a few secrets of his own , a past that haunts him daily. The tension between them and let’s talk about slow burning and yearning! 🤌🥵

Overall this was a quick and incredibly entertaining read. Anxious for book two!

[Grace Bhatia · Rating 2 out of 5]

I had a hard time connecting with this one. The FMC and MMC’s back-and-forth, along with their inner dialogue, became repetitive and I struggled to stay invested since it felt like things kept circling the same ground. My current reading slump probably didn’t help. Overall, there’s nothing insanely bad here I just didn’t end up feeling much for the story or characters this time. However, the ending really caught me off guard. I was not expecting that! 😮