General Pratt, a national security chief, and his aides approach Dr. Bartholomew Snow, a successful psychiatrist, to assist the U.S. government in secrecy.

General Pratt hides the patient, Arthur Vincenti, in a remote place known only as "Base X", forcing Dr.

Enemy agents and an organization who kidnap and sell scientists to the highest bidder want to know what Vincenti knows, so he is in danger.

When she has the doctor arrested, Snow, in order to keep the Vincenti affair secret, tells both the authorities and the press that he and Vicky are engaged to be married and are actually having a lovers' quarrel.

But soldiers arrive in airboats and place Fitzpatrick under arrest, leaving Vicky to consider whether she would like her make-believe engagement to Dr.

[2] In June 1961, 20th Century Fox bought the screen rights and assigned the project to producer David Helwell.

It was reactivated in September 1964 by former press agent turned producer Marvin Schwartz, who set up the project at Universal with Rock Hudson attached to star and Phil Dunne to direct.

[8] Florida second unit scenes were shot in February 1965 at Paradise Park on Silver River, Sharpes Ferry Bridge, Indian Lake and at the Silver Springs Airport with members of an Ocala, Florida, community theatre group called the Marion Players acting as stand-ins and doubles for the principal actors.

Snow finds the secret base using only sounds that he heard on the journey were used in Joe Smith, American and its remake The Big Operator, and were borrowed for an almost identical scene in the 1992 film Sneakers.