Ensign Charles Parker (Tim Conway), newly assigned to the PT 73 crew as Executive Officer, is Captain Binghamton's (Joe Flynn) last hope to tame McHale (Ernest Borgnine) and his "pirates".
McHale and the boys go all out to try to help Parker win the attention of Lt. Casey Brown (Betsy Jones-Moreland), a very attractive nurse he's infatuated with.
McHale, Nurse Molly (Jane Dulo), and the 73 crew must practice some trickery to keep Binghamton at bay, while they arrange for an against-the-rules wedding for Christy (Gary Vinson), PT-73 Quartermaster; and his fiancee, Lieutenant Gloria Winters (Cindy Robbins).
While out on a recon mission, McHale and the 73 crew discover a deserted plantation, which they turn into a party house where they can enjoy themselves when not on duty secret from Binghamton.
Parker mixes business with pleasure on Emile Gerard's (Marcel Hillaire) island plantation.
Later, he must pose as a Frenchman in order to avoid capture while he reports details on a Japanese radio-jamming operation.
McHale and the crew must then scheme to get out of jail, find Frenchy, and get the 73 back before Binghamton returns from a staff meeting.
Christy has a chance to hear his little girl call him Daddy, courtesy of a ham radio operator (Phil Arnold) in the States.
Ordered to provide a safe haven for a Sultan (Henry Corden) and his three daughters, Binghamton is forced to send McHale and the 73 crew to rescue the royal family and bring them to Taratupa.
But when a potted-plant hits Binghamton in the head making him woozy, McHale thinks of a plan where they can get the recorder back.
But McHale manages to stay out of trouble when he and his look-alike Italian cousin, Giuseppe, assume each other's identities long enough to fool Binghamton and General Grayson (Willis Bouchey).