SPOILERS! This has one of the most complex/convoluted plots of any HB book and deserves 5 stars just for its wanton audacity. Verily I say unto thee: you have to read it to believe it.
It turns out that the mystery is actually three mysteries, so I would like to challenge future readers to study the explanation of each mystery, unraveled below, then read the book to see how the author actually pulls this crap off.
Mystery #1: Karel Tabor’s assistant Xavier wants Karel’s job as head honcho architect, but Karel’s fresh-out-of-college son John is so awesome that John will most likely get the job when Karel retires. This is bad news for Xavier, but he’s already a bad guy since he has caused engineering disasters at three of Karel’s projects in order to defame Karel and cause his early retirement. Xavier, therefore, has a plan to defame John: causing him to go crazy and make him think he’s suffering from his family’s werewolf curse; using a nurse at John’s sanitarium the plant micro speakers in John’s room from which Xavier can speak to John, thereby making John think he’s hearing voices; and, having the nurse hypnotize John so that he will go into a trance whenever he hear’s a wolf howl, thereupon walking zombie-like to a secret cabin in the woods. While John is thus hidden, Xavier perpetrates incidents around town that he makes sure are blamed on a werewolf. Xavier even dresses up his Doberman Pinscher in a suit of glow-in-the-dark animal fur and makes sure people see it. He plants rumors in local media about the Tabor curse, and even dresses up as a wolfman himself and scurries around the woods near a Tabor family cookout.
But two complications arise for Xavier. First, his boss Karel figures out that Xavier is the cause of the three engineering accidents and forces Xavier to confess his crimes on an audio tape. Karel locks the tape in a safe and swears not to reveal Xavier’s crimes in return for his promise to reform himself. Xavier then hires an ex-con, Bubbles Upton, son of a rival architectural firm magnate, to break into the safe and steal the recordings. Xavier helps Bubbles by hiding the safe’s combination (and a map of where it is) inside a lunchbox conveniently placed on the 25th floor of an under-construction Manhattan skyscraper, which Bubbles will have to retrieve by scaling along a grappling hook’s rope thrown from the window of an adjacent building (Bubbles will eventually open the safe with explosives).
The second complication to Xavier‘s plan is when Karel hires the Hardy boys to figure out what’s wrong with his son John. Xavier then goes to Bayport, follows the Hardy Boys to a restaurant, secretly steals Frank’s jacket so that Xavier‘s ersatz werewolf (the Doberman) can find and attack the boy. And, for good measure, Xavier shoots a silver bullet into the side of the Hardy’s house.
Did you get all that?
Mystery #2: Gustav Tabor is an elderly, distant, Czechoslovakian relative of Karel and John Tabor who wants to will his vast fortune to a worthy family member. Gustav’s only European heir is a Frenchman, Paul Clermont, who is unworthy of Gustav. So, Gustav hires an American private eye, Elmo Yancey, to investigate whether John is worthy to receive his millions. Clermont, knowing of the Tabor werewolf curse, comes to the U.S., learns of the werewolf scare centered around John and that John was once in a sanitarium. Clermont secretly informs Yancey about the sanitarium info so he will investigate and report it back to Gustav. Meanwhile, he finagles the sale of a taxidermied wolf, removes the skin and sews straps onto it, as if it can be worn. Clermont then hides it in John’s cabin and tips off the sheriff that he can arrest John for the werewolf troubles by finding evidence in the cabin.
Mystery #3: Dark Eagle was an Iroquois Indian who fought on the side of the UK during the Revolutionary War. For his service, he was taken to London where he met King George III and received a tomahawk made of silver and encrusted with jewels. The tomahawk later went missing, but it turns out it’s somewhere underneath Dark Eagle’s porch. His descendant, Hank Eagle, works for Karel Tabor and becomes concerned when a mystery man starts asking whether he has found the tomahawk yet. As I recall, having just finished this book, the mystery man looking for the tomahawk comes to nothing and he never appears again. But I could be wrong since there is so much happening in this book and I just missed it.
Also, Chet builds a boat.