McGee becomes a fireman over the protests of his mother, who doesn't want to see her son sacrifice his life the way his father did. When she dies, McGee adopts little Elizabeth Stevens, who takes care of him instead of vice versa. Along the way he meets Agnes Evans, a chorus girl, and falls in love.

John Livingston is a rich mama's-boy, who owns a blooded dog named Paul. Paul meets Maggie Mutt, and Paul, being a pedigree canine and somewhat of a cad, lures trusting Maggie to the barn to have his way. He then departs for his palatial doghouse at the Livingston estate. Meanwhile Maggie is broken-hearted and also finds that she is in a "family way", and gives birth to a pup she names Hank. Maggie tells Hank to find his "human ", and departs the scene. Hank goes to the park, meets a "human" named Mary Kelly, who is a homeless waif and sweetheart of poverty, and the two adopt each other. Later on in the park Paul comes strolling along with his 'human', John. A child falls into the lake and Paul and Hank team up to save her.

In the early 1900s, a bull terrier living on the streets of the Bowery rises from a street-tough engaging in dogfights to pedigreed show dog among the upper crust. All the while, he has two ambitions--to be reunited with his mother and to get even with his father who deserted her.