The Police Dog, snooping around, comes on a familiar scent and follows the whiff of an old acquaintance to a butcher shop. The Senegambian presiding shies a ham-bone at him. There's no "bonework" about the Pup's catching ability, however, and he scampers off to gnaw at leisure. He meets up with a mastiff, who takes charge of the bone, much to the Pup's sorrow and righteous anger. Meantime, the butcher, hearing a noise outside, and thinking it to be the recurrent Pup, flings out a weighty bone that knocks a cop senseless. The Pinkerton Pup chases the mastiff into a large water-main, but comes out considerably mussed. It was a "pipe" for the mastiff, who runs from there into a watchman's shanty. The Pup blows three shrill blasts that wake Officer Piffle on his beat. Piffle rushes in, and is tipped off by the Pup that a thief lurks within. Piffle rushes in and when he rushes out again, it is with great speed, and in full dress, for a Turkish bath. But in the scuffle, the Pinkerton Pup manages to connect with the bone, and is last seen cavorting brightly on for parts unknown.
—Moving Picture World synopsis