When young inventor Bob Moore fails in his efforts to provide his father, a safe manufacturer, with a lock that is burglar proof, he contacts The "Eel," the most talented safecracker in the city, to offer him a job in his factory. The Eel, deciding to go straight, accepts the offer, but when he later learns that Irene Hardin has been given a valuable necklace by her father, The Eel plans one last job to secure Irene's pearls.