A young, beautiful prostitute named Sadie Thompson arrives on the South Pacific island of Pago Pago looking for honest work and falls for Timothy O'Hara, an American sailor who is unfazed by her unsavory past. However, Mr. Davidson, a missionary who arrived on the island at the same time, aims to "save" Sadie from her sinful life and petitions to have her separated from her beau and deported back to San Francisco.

Bob and Jim Whitely are twin brothers. Bob, an army veteran who suffered shell shock in the war, escapes from a sanitarium and holds up the Express train, for which Jim is mistakenly arrested. Jim soon escapes from jail in order to find his brother. However, his task is complicated by a crooked sheriff who pins a holdup and murder on him that the sheriff himself actually committed. To make matters worse, the murder victim was Tommy Wilkins, the brother of Jim's fiancee, who now thinks that Jim killed her brother.

The Allen spinsters adopt Bradley Nickerson, who grows up with Gussie Baker, the little girl next door. Fifteen years later he is first mate of the Thomas Doane, owned by Granny Baker. A plot to sink the ship is averted by Bradley and a sailor, but ultimately the ship is sabotaged.