A psychiatrist with intense acrophobia (fear of heights) goes to work for a mental institution run by doctors who appear to be crazier than their patients, and have secrets that they are willing to commit murder to keep.

In preparation for Operation Overlord, the Allied invasion of Nazi occupied territory, the ‘overlords’ were the few Allied agents who knew the details of the operation. When one them is captured by the Germans, a double agent must infiltrate occupied Paris, with the help of a high level German officer and the French Resistance.