Two sisters from Indiana, the wide-eyed and innocent Mae Thorpe, and her more streetwise sister June, move into the Rolf House for Homeless Girls in New York. With June's help, Mae obtains a job as a stenographer for the scientist Joseph von Schraeder, while June gets work as a telegraph operator at Western Union.

A variety of broad-painted and unlikely characters are trapped in an underground café when a Mississippi River levee breaks and causes flood havoc above and below.