Summary for my reference:
Number 16: The Vessel - We are introduced to the bad guy organization Kara with a scene where they are all having their little villain meeting via projections (exactly like the Akatsuki). They're talking about losing a "vessel." An old man in the group is pissy about things, and he gets a visit from another person in the group, who kills him.
We skip on to a duel between Boruto and Naruto. Naruto wins, of course, and he reveals the use of his prosthetic hand. They're testing out ninja tools, and he is able to use his hand to absorb jutsu. Then they have a meeting, where Naruto explains to Boruto and his team about Kara, how the members have marks similar to Boruto's, and they discuss ninja tools.
Another scene shows a crashed blimp and Konohamaru and a squad investigating and finding an empty coffin on board.
Number 17: Ao - Konohamaru copies data from the blimp onto a Ninja Scroll Flash Drive (lmao) when his squad is suddenly attacked.
More talk in the meeting with Naruto, Boruto's mark, and the organization Kara, whose members supposedly have ohtsutsku-level abilities. We are reintroduced to Tohno Katasuke, a scientist who is working on developing ninja tools. Boruto immediately dislikes him due to the fact that he gave Boruto the tool he used to cheat during his chunin exam. Naruto sets the team up for a mission to occompany Tohno to deliver his prosthetic hand to a research facility in another town. Boruto storms out and Sarada and Mitsuki have to reel him back in to the mission. Boruto is pissy because he got in trouble for cheating with a ninja tool, so he thinks they are all bad. Naruto tries to explain to him that they are not inherently good or bad, it depends on how you use them (and using one in the chunin exams was cheating).
The group takes a train, where they meet Lord Ao, someone Tohno knows because he made him a prosthetic arm and leg. With a screwdriver, Ao demonstrates to the skeptical Boruto that tools are not inherently anything, it's all in how you use them. After the group disembarks, a member of Kara is revealed to have been sitting behind Ao the entire time, and they are in league; Ao is apparently an "outer" member of the group. Here we find out that Ao had previously used genjutsu on Tohno to gather information about what the Leaf Village is doing with ninja tools. The Kara member leaves a box with intel and weapons for Ao and instructs him to retrieve the "vessel" they lost.
Number 18: The Hand - The group brings Naruto's prosthetic hand to the research laboratory, where we meet Inuzuka Akita (top notch researcher) and Kakei Sumire (previous classmate of Boruto's who decided to forego the chunin exams and become a researcher instead). Akita has the squad test out different ninja tools and we meet her ninja dog, Chamaru, who has a prosthetic leg. Boruto warms to the idea of ninja tools and the importance of science to the ninja world. He gets a call from Naruto, who explains that Konohamaru is nearby and out of contact and their squad is the closest so they need to go investigate.
Number 19: Puppets - Akita gives the squad some ninja tools and healing foams, and Tohno arms himself with a robotic suit of armor. Chamaru also joins the group. Before they set out, Sumire hints to Sarada that she has a crush on Boruto.
The group arrives to the scene of the crashed blimp and finds puppets lying around. They engage the puppet in combat and discover that they are autonomous ninja tools. Tohno figures out how to overload them by getting them to attack but then absorbing the attacks. Tohno knows that the reason the enemy has these ninja tools is because he was put under a genjutsu. Chamaru leads them to a nearby cave, where Konohamaru and one of his squadmates are hiding out. Ao makes a dramatic appearance, demanding the whereabouts of the coffin's contents (the vessel, though we have not seen it yet) and whipping out a machine gun.