A gambling addict persuades his brother-in-law to go on a cruise to snare wealthy women and con them out of a few bucks...but fails to tell him that the two will be waltzing their way across deck as the cruise dance instructors. Jack Lemmon, Walter Matthau, Dyan Cannon, Gloria De Haven, Brent Spiner, Elaine Stritch, Hal Linden, Donald O'Connor, Edward Mulhare, Rue McClanahan.