Mary Beth is a marine biologist that gets annoyed when a dog called Zeus stows aboard her research boat. Nevertheless she is intrigued when the intrusive canine makes best-friends with her captive dolphin, Roxanne. She falls in love with Zeus’s owner, Terry, a musician who rides a bike.

In this film based on a Neil Simon play, newlyweds Corie, a free spirit, and Paul Bratter, an uptight lawyer, share a sixth-floor apartment in Greenwich Village. Soon after their marriage, Corie tries to find a companion for mother, Ethel, who is now alone, and sets up Ethel with neighbor Victor. Inappropriate behavior on a double date causes conflict, and the young couple considers divorce.