Herbert Moore is the leader of a gang of crooks. He leads by sheer force of mentality, while his pal, Burley Butts, leads by brutal force. Between them they have a plan to rob Mr. Stanhope, a noted philanthropist, on whom Moore has been spying. For their ill purposes they use little Oliver, an unwilling pupil of Butts. On a dark night they embark on their venture. Gripping events succeed each other in rapid succession. Oliver enters the house. He makes his way, with a bulls-eye lantern; here we have a remarkable light effect, a sudden flash, the lights go up, and little Oliver faces the muzzle of a revolver. Mr. Stanhope is surprised to see the youthful criminal. He quizzes him. But little Oliver cries and tells his story. Stanhope is moved by the boy's tale. In taking out his handkerchief to dry his eyes, Oliver drops a silver half-dollar. Mr. Stanhope attempts to return it to Oliver but the child brushes it away and tells him to keep it, informing Stanhope that the silver half-dollar is the insignia of the gang and that it can open in the middle and be used in an emergency as a saw with which the user may cut rope, wire or glass. Stanhope's interest is aroused, and he places the little souvenir in his pocket. Later this piece of metal is one of the means of saving his life. Oliver then pleads to be let free, and Stanhope allows him to go, after taking an oath that he will not attempt to steal again. This attempt failing, the gang sets a trap for Stanhope, but little Oliver passes a note and key to his benefactor when the thugs lower him into a vault. When Stanhope finds himself in the narrow vault, he struggles hard to free himself from the bonds which almost cut to the bones. He frees himself sufficiently to get the silver half-dollar, which he now puts to good use. After hours of effort he breaks his bonds. He tries to straighten himself and then finds the heavy key and the note in his coat pocket. He is scarcely able to read the instructions. The greenish light gives him the appearance of a man risen from the dead. Gradually his dulled mind absorbs the portent of the note. He desperately feels for the secret keyhole. His search is not in vain. Presently, he swings back the granite door and he is confronted with a vista of the city's filth and slime. He crawls through the outlet and makes his way through the sewer channels. The stench from stagnant sewerage pools, cesspool waste, mud and dirt, nearly suffocates him. But on and on he struggles, up to his knees through this liquid filth. Even an attack by a horde of sewer rats does not swerve him from his path. He fights the rodents off and they scamper. At last, weary and exhausted, he finds his way to the sewerage main, a ladder leading to a manhole giving entrance to the street. Bespattered with mud and filth, disheveled and bedraggled, he rushes through the streets and to the police station. The gang is soon surprised by big Colt six-shooters and little Oliver and his brother find a home in Mr. Stanhope's happy household.