So having Fielding on board gave them the chance, for really the first time, to use a perfectly natural gap between stories for further adventures. However, in what was on the surface a slightly odd move (though in reality seemingly due to the whole reunion being down to Mark Strickson's suggestion) they decided to set these new stories using another, equally contrived set up by having Tegan travelling with Nyssa and Turlough. A trio that were only all together on TV for two stories as part of a big story-arc with little possibility for side steps between them.
To deal with this, these stories are actually set after Nyssa departs in Terminus, with her rejoining the crew by accident in what for them is just a couple of weeks but is for her 50 years. Despite being slightly forced this has wound up the most interesting thing in these first two trilogies. Though the first year ignored Nyssa's age and mission (she's out to cure a deadly plague sweeping the galaxy in her new home time) almost completely after the first story to the point the third play even had characters lusting after her as is she was still a perky young woman, 2011 has brought this much more to the front.
So we have an older, more world weary Nyssa keen to return to her family and her quest but who is also finding her old lifestyle seductive. With Sarah Sutton's acting having come on in leaps and bounds both since her days on TV and her early, hesitant Big Finish appearances (which were after all, her first acting in a long time), there's an interesting and thoughtful character arc set up that, though not resolved here, does move on considerably.
The Tardis arrives underground in an old secret government facility that doubles as a bunker in the event of a nuclear war on election day in 1983 (not only is this roughly around the time the stories this is set between were made it's roughly contemporary with the earliest of James Herbert's Rats books, the third of which was set in an underground nuclear bunker as well). The place is about to be shut and the castle above given to English heritage, so you have a team of soldiers (all but one dead before the story starts) led by a civil servant and his PA clearing the place of paperworks and a journalist and two campaigners breaking in to find the dark secrets that are supposed to be hidden there.
Which turns out to be that back in the 60's a Dr. Wallace (main guest star Terry Molloy in a performance as a mad scientist of a very different sort to his usual Davros role) tried to create super intelligent rats to work as spies, even joining three as a Rat King who coordinate the others telepathically. As is always the way this these things they get too smart, escape, take over the underground base and turn most of the scientist into mindless half man half rat servants, except for Wallace who gets to keep his mind so they can torture him for shits and giggles. With their domain about to be sold off they've now decided to unleash a plague they've created on all humanity to wipe them out once and for all.
The Tardis crew is very quickly separated (mainly due to Davison and Strickson not being able to work on the same days). Nyssa winds up with a relatively nice rat scientist who only wants to enslave humanity by making them docile rather than killing them (splendid chap), and he seems to co-opt her help by offering their own research in plague development that may help provide the cure that she herself has been looking for. Of course, she plays for time and doesn't do him much help, but she and her furry friend do wind up with a good, if fraught, working relationship and his mistreatment by the other rats for disobeying orders, that results in him having his intelligence stripped away by a “Punishment” virus, is extremely nasty.
Turlough stays in the Tardis with the PA, Sally Lucas and has to escape and fight off some rats who manage to get into the ship. In a nice bit of continuity he uses a futuristic defibrillator left over from last year's The Whispering Forest as a defensive weapon. But when Lucas turns out to have been in league with the rats all long (being keen to be one of the few survivors, she also seems to think sexual discrimination in the work place is a good enough reason to kill everyone else) her attempts to turn it against him backfires thanks to the Tardis' state of temporal grace, which can apparently tell the difference between defensive and offensive action. Lucky for Turlough, but then, exactly how that works (if at all) has always been just a little vague anyway.
Tegan does less well than the other two, mainly being locked up with Wallace so she can have the plot explained to her. There's a nice sinister moment where she witnesses one of the people who broke in, a failed squadie, Kevin, who didn't see action in the Falklands put on a giant wheel which electro-shocks him every time he slows down. This supposedly generates electricity, but it's hard to discount the idea it's all for more shits and giggles.
Tegan does get to escape and get recaptured as is the way of all Doctor Who companions, during which she finds out the civil servant, Andrews, is also in league with the rats. For even less sensible sounding reasons than Lucas, he seriously seems to think they'll make him President of Europe after they've taken over (!). When he finds out the truth about the plague he has a brief moment of defiance before just shrugging his shoulders and sort of going along with it.
The Doctor also manages to be a bit sidelined, spending most of his time wandering up and down corridors with the journalist, Catalin Jones (who turns out to be Wallace's daughter, and goes from hating him for his animal experiments to being reconciled and deeply upset over his death in the blink of his eye) and the other campaigner, who dies an ignoble death when the path collapses under him.
The Doctor does get a good confrontational scene with several of the rats where he manages to bluff them that a dog whistle could destroy their mental link, and this inspires him to build something bigger out of reel to reel tape recorders and other gubbins that will do the job for real. With this and the Punishment virus that's been duplicated by Nyssa Wallace is able to atone for what he's done by de-evolving the Rat King and then blowing up the entire place courtesy of an electrical fire and some dynamite Kevin kindly brought with him. The Tardis crew leave, but with Nyssa depressed by her failure to find a cure despite what she went through.
Rat Trap is Lee's first audio drama (he normally works in comics and has spent the last few years working on IDW's Who comics) and there are places this shows with characters describing what's right in front of them for no readily apparent reason. Most blatant when they first see the mutiods and feel compelled to go into depth on the rat fur and augmentations on them. Other than that though this is mostly a very accomplished play, the idea is a neat (if well trodden) one with the rats being nicely realised without being silly. Nyssa's dilemma and the fact we never really get a firm answer how far she'd have gone with the pacification plan if the Doctor hadn't sorted things out is also extremely.
There are some flaws however. Tegan is somewhat wasted, especially considering the dramatic potential in her confronting Nyssa over helping the scientist even slightly, there feels like there's a great missing scene there that would have really given Fielding something meaty to get her teeth into.
The human collaborators are also poorly sketched, though they've been forced into working for the rats they seem tremendously keen on being slaves amongst the rubble of human civilisation for fairly nebulous reasons, was sexism really so bad in the '80's any working woman would be fine with all humans being killed dead as payback?
It's also not really explained how the rats were apparently able to “lure” many people down to their lair to add to their original cache of scientists (though at least Lucas and Andrews had reason to go down there), nor how they performed the original operations to alter people without opposable thumbs.
However, that's not enough to counter a strong, sinister atmosphere, some great performances and well written dialogue (I especially love Tegan's reaction to finding Lucas tied up on the Tardis floor). As a first effort in the audio medium it might have some rough edges, but shows a lot of potential that suggests Lee might have a great future at Big Finish, and the dangling thread over Nyssa nicely sets up things for next year.
Three super intelligent killer rats out of five.