A group of archaeologists asks Tarzan to help them find an ancient city in a hidden valley of women. He refuses, but Boy is tricked into doing the job. The queen of the women asks Tarzan to help them.

Based on a play by Phoebe and Henry Ephron, "3 Is a Family" is a 1940s farce. Charlie Ruggles plays a hubby whose bungled business schemes force his wife, Fay Bainter, to enter the workplace. The couple's daughter, Marjorie Reynolds, shows up with her twin babies in tow. Son Arthur Lake arrives with his pregnant wife (Jeff Donnell). And overbearing maiden aunt Helen Broderick also decides to move in. Because his wife is away at work, poor old Charlie Ruggles is not only housekeeper, but nursemaid and servant as well.

Two zanies get mixed up with a Southern colonel, his beautiful daughters, a nightclub and a haunted mansion.