 At Sinclair 's home , Jenny discovers that he is a Nazi secret agent , and Jenny knocks him out . She is later detained and forced to leave a message for Cliff to bring the rocket pack to the Griffith Observatory in exchange for her life . Just before he is arrested by the FBI and taken to Howard Hughes , Cliff hides the rocket pack . Hughes reveals his rocket pack is a prototype , similar to one that Nazi scientists have , up to now , been unsuccessful in developing . When Secord asks why there is so much interest in the rocket pack , Hughes shows a horrifying propaganda film depicting flying soldiers invading the United States and hoisting a Nazi flag over the White House . When Hughes demands the return of the rocket pack , Cliff explains that he needs it to rescue Jenny ; he escapes , inadvertently leaving behind a clue to where he is headed . 
