Mrs. Pittman's well-to-do Pittsburgh family didn't approve of her marriage, so the young bride moved away and lost touch with her relatives. Years later, she has returned to her native city as a widow and now runs a boarding house, one of the only jobs available to respectable women in the early twentieth century. Rooms at Mrs. Pittman's place are cheap because of the annual floods from the Allegheny River, which inundate the building's basement and first floor. Ordinarily, the overflowing waters are just a mild nuisance but this year the flood takes a sinister turn when a headless corpse emerges from the waters.
One of Mrs. Pittman's tenants, actress Jennie Brice, has disappeared and the landlady is certain not only that the unidentified body is Jennie's but also that Jennie's husband is the killer. Lacking evidence, the police have dropped the case but Mrs. Pittman's discovery of a broken knife and blood-stained rope are enough to strengthen her resolve. An eager young reporter and other amateur detectives join Mrs. Pittman in her crusade to solve the crime, and their efforts lead to a budding romance that might help bring the lonely landlady back into the family fold.