A couple of college students, American Alex Campbell (David Ladd, brother of one of the films executive producers, Alan Ladd Jr.) and Brit Patricia Wilson (Sharon Gurney), are returning from a date late one night, and notice a seemingly well to do man lying unconscious on the stairs leading out of the subway station. Alex doesn't want to get involved, but Patricia insists they tell someone, so they tell a policeman, but by the time they get back to where they saw the man he's gone. Alex had taken a peek at the man's wallet, so passed the name on to the police. The local Inspector (Donald Pleasence) is initially uninterested in the report (as there's no body, and no missing person reported), but when a check is run on the name and it is discovered to belong to a holder of the Order of the British Empire, a senior civil servant in the Ministry of Defense, the inspector becomes much more interested.
The film follows the Inspector and his associates in the investigation, the couple who first found the man, and his murderer. Christopher Lee stops by in a camo role (which he agreed to do for scale as he had never worked with Pleasence before and wanted to) as a member of MI5 who shews the Inspector away from the case. But whatever secret goings on the missing man was involved with turn out to be unrelated to his disappearance.
The "twist'' of the film is that the missing man (James Cossins) was knocked unconscious and later retrieved by a cannable (Hugh Armstrong). The station in question is located near a long-abandoned tube line that had collapsed in on itself during construction, back in the Victorian era. At that time, it was standard practice not to dig the dead workers out as it was deemed not worth the effort. Here however a number of the male workers and for some reason some women survived the collapse, and again for some reason they didn't dig themselves out and return to the world but formed a small colony that survived for eighty-odd years, picking off as needed fellow members of the lower classes to eat. This apparently didn't attract attention because those that the cannibals picked off were deemed unimportant by the police and upper classes. The class commentary here is heavy handed.
The colony was at last down to one member, and because by chance he abducted someone deemed important (who was down there trying to hire a prostitute), the larger mystery finally came to light. The killer was essentially a caveman, who could communicate only in grunts and slivers of English that had survived underground. The "good guys" kill him in the end, but projecting forward this case would have become a tabloid sensation and prompted investigations into the better part of a century's worth of crappy police work.
So yes, the mystery proves to be silly, but the film does a good job of maintaining tension and boasts some interesting characters. For me the most interesting by far is Pleasance's Inspector Calhoun, there is a lot of implied backstory to the character and Pleasance elevates
him with the particularities of his performance. He's a man who given his age would almost certainly have served in The War. He lives alone and apparently never married, he's very particular about his tea, is kind of a grump, has some sort of ongoing beef with Lee's MI5 character, and as an investigator, I'd give him a B -.
This is another movie I didn't expect to finish, just wanted a taste of it. However, it proved interesting enough to catch me and hold my attention for its 87 minutes. Smarter than it needed to be, its exploitation far that is just enough off the expected path to be memorable. **1/2
