Five young girls want to embark on a Mediterranean cruise on the motor yacht "Rosebud". The ship belongs to Charles-André Fargeau, head of a company, whose granddaughter Sabine has invited the girls on the cruise. With the help of a crew member, members of the Palestinian terrorist group "Black September" get onto the ship and abduct the women.
The CIA gets involved and sets British undercover agent Larry Martin on the kidnappers.
Robert Mitchum was originally supposed to play Larry Martin, but he gave up or was fired after he and Preminger clashed. Appearance for Peter O'Toole. Probably in anticipation that picky viewers would wonder why a CIA agent looks and sounds British, the script explicitly calls Martin a "mercenary". The implication is that he is a freelance employee and not technically a CIA employee with US citizenship.