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.

A journalist finds his life is in danger when he investigates the death of a woman who was involved with a religious cult.

Allied agents infiltrate the Nazi rocket complex at Peenemunde in order to obtain their secrets and sabotage the plant. The film alternates between German developments of the V-1 missile and V-2 rocket (with a German cast speaking their own language) and discovery by British Intelligence of the weapon.