There's something pretty grisly going on under London in the Tube tunnels between Holborn and Russell Square. When a top civil servant becomes the latest to disappear down there Scotland Yard start to take the matter seriously. Helping them are a young couple who get nearer to the horrors underground than they would wish.
A Scotland Yard detective is investigating a string of robberies and a murder, and the information he uncovers leads him to the estate of a wealthy but strange English family, who share their mansion with a group of nuns. The detective comes to suspect that neither the family nor the nuns is quite what they seem to be.
