The U-Boat Mystery is designed to be played by between three and five Troubleshooters. Between them, they should have some decent combat skills and one of them at least, should have the Diver ability, if not the Divemaster ability, as the scenario does end in a dive on a submarine. One option might be to let the Troubleshooters have the opportunity to train before the dive itself and spend any Experience Points at that stage of the adventure rather than afterwards.
The U-Boat Mystery opens with a discussion of the Plot Hooks which will get the Troubleshooters involved in the scenario’s mystery. The four are Arch-Enemy: The Octopus, Do-Gooder, Looking for a Case, and Media Darling, and one or more of the Troubleshooters have these as one of their two Plot Hooks, enabling them to get pulled in from the start. This is a feature of The Troubleshooters and each of the Plot Hooks can be used in two ways. Either as a handout which relates the events of the Plot Hook and can be easily shared with the other Troubleshooters, or as a scene in their own right which can be played out as a prequel for each of these Player Characters, ideally before the opening credits roll… For the Troubleshooter with Arch-Enemy: The Octopus, a widow, Mrs Wallhaus gives him a map of the Sitomeyang archipelago in Southeast Asia, before she is suddenly shot and injured; for the Do-Gooder, he helps evacuate the tenants of a burning apartment block and learns that someone heard shots before the fire and that the only person missing is a widow; the Troubleshooter Looking for a Case receives an anonymous bundle of clues, all seemingly unconnected; for the Media Darling, the journalist—Pierre Martin—mentions that he is off to New York and then the Far East to cover a German marine expedition, but is then kidnapped. The Game Master does not use all four, but picks two to tie in two of the Troubleshooters cast and then their players should do their best to pull in the others into the mystery. Of the four Plot Hooks for The U-Boat Mystery, all of which are set in Paris, one of them should definitely involve Pierre Martin.
Once the Troubleshooters are on the trail of Pierre Martin, a journalist for La République, they will find further clues. These include a u-boat lost at the end of World War 2 on a long journey from Germany to Japan, a painting influenced by Wagner and said to be liked by Hitler on display as part of an exhibition in New York, a marine biology expedition being mounted by the University of Hamburg to South East Asia, and more… It should be relatively easy for the Troubleshooters to put these clues together and follow them to the island kingdom of Sitomeyang. There are side clues which though not key to solving the mystery, will help the Troubleshooters and better prepare them for events later on. These will take the Troubleshooters to Hamburg and possibly Berlin, but whether they travel to either city, or indeed to New York, their ultimate destination is Sitomeyang.
In Sitomeyang the Troubleshooters will need to track down the final resting place of the missing u-boat and then make the dive. The final scenes of The U-Boat Mystery involve them diving down to, gaining access to the submarine, and exploring it, perhaps after having sneaked aboard the marine biology (or not) vessel for further clues and probably during a confrontation with the rival dive crew. The dive and the exploration of the submarine is described in some detail and will require some careful planning upon the part of the Troubleshooters as it is technically challenging and could get them into serious trouble if it went wrong. The confrontation is excitingly staged and makes for a great climax in the mode of the underwater scenes from the James Bond film, Thunderball. Throughout the whole of the adventure, the Troubleshooters will find themselves watched, harried, and even attacked, only adding to the tension and excitement of the adventure.
In terms of support for the Game Master, The U-Boat Mystery comes with eleven NPCs and sixteen enemies—one of whom is weird indeed! Besides the four start-up handouts, The U-Boat Mystery includes seven clues and handouts, as well as deck plans for both the enemy ship and the submarine. Details of the city of New York—including such information as Fiddler on the Roof having just opened, and the fictional kingdom of Sitomeyang are provided in the same format as the city descriptions in the core rulebook, meaning that they can be revisited again and again. Similarly, the new gear kits can also be used elsewhere.
Physically, The U-Boat Mystery comes as a handsome hardback, presented in full colour, with some fantastic artwork done in the bande dessinée style. The handouts are very nicely done—the book actually comes with a handful of tourist visas for Sitomeyang!—though the deck plans of the submarine and the boat belonging to the rival marine biology could have been clearer. However, the scenario does feel as it could have been better organised to be a clearer read for the Game Master, certainly in the opening stages when explaining the various clues. One aspect of The U-Boat Mystery which is optional is its Science Fiction elements. The mystery does involve Nazi fringe science and its side effects as written, although neither is crucial to the plot, and they do send the scenario off in a slightly wacky direction.
The U-Boat Mystery is overall, a very nicely done scenario. Neither its mystery nor its clues are particularly complex, meaning that the players and their Troubleshooters can concentrate on the action and the roleplaying as they round them up and put them together. Every Game Master of The Troubleshooters will want to grab The U-Boat Mystery for her campaign because the scenario is exciting and fun, and the players and their Troubleshooters will thoroughly enjoy themselves.