Charlie’s (Matthau) predilection for playing the horses has put him at the end of his financial rope, courtesy of his friendly bookie. It isn’t long, though, before he dreams up another “can’t miss” scam. He talks his understandably skeptical brother-in-law, Herb (Lemmon), into joining him for what Charlie promises will be the most luxurious vacation of their lives, aboard a Caribbean-bound cruise ship.

But Charlie has left out a few, well, “minor” details. For one, their accommodations are located deep in the bowels of the ship; in fact, there’s barely enough room for them to stand. Secondly, to earn free passage, Charlie has volunteered them for duty as dance hosts. Charlie, of course, does not dance, so Herb, who is an accomplished dancer, is left facing the dozens of eager ladies on board ready to “trip the light fantastic.”