Private detective Bill Reardon is awakened one morning by his dizzy wife Sally, who cannot remember what the string tied to her finger is supposed to remind her of.

Meanwhile, Crenshaw shows up at the Reardon detective agency and wants to hire them to find out why he is being followed by an unknown man who recently searched his apartment.

Believing Crenshaw is innocent, Sally quickly leaves the restaurant so she can call the young clerk at the jewelry store and warn him.

Davis is seen leaving the nightclub, and he deliberated picks up a note at the hat check stand which was left for Tony Croy, a known mob boss.

In the cab, Davis reads the note he stole, which gives the location of some unnamed object in a specific filing cabinet at the store.

When Croy comes to Mrs. Nacelle's mansion to collect the stolen jewels, she tricks him by having him open a safe which is rigged to fire a gun attached to a device inside.

Bill and Sally Reardon set a trap for Mrs. Nacelle, solve the case, and lead the police to a final showdown with the murderous wife.