The German underground has a Gestap spy in their midst. He has a plan to destroy the resistance completely, and it's tucked away in Klink's safe. But Fraulein Hilda is on leave, and General Burkhalterr's sister Frau Linkmeyer is filling in. She plans to work all night, and the Hogan crew can't have that. Hogan comes up with a plan to have Klink try to romance her and keep her busy while they steal the plans and try to uncover the mole.