An impoverished woman exits a charity hospital with a newborn she conceived with a struggling artist. Because she is poor and the baby's father has no interest in raising the child, the woman abandons the infant with a note instructing whoever finds him to take care of him. After spotting an expensive car parked nearby, she leaves the baby in the back seat. Unfortunately, before the owner of the car returns, the vehicle is stolen, complete with the abandoned baby.
When the car thieves discover the child, they are shocked and leave him on the side of the street, where he is found by The Tramp, played by Charlie Chaplin. At first, The Tramp wants nothing to do with the child, and tries to pass him off to someone else, but he eventually softens. Meanwhile, the child's mother has begun to feel guilty and changed her mind about giving away the baby, but is upset to find the car where she put the child is gone.
Five years later, the child has become The Tramp's partner in crime, which usually involves scamming their neighbors. The child's mother has become a big star and is now very wealthy. When The Kid falls ill and a doctor comes to treat him, it comes out that The Tramp is not his real father. The Tramp shows the doctor the handwritten note the child's mother left pinned to him, but the doctor takes it and hands it to the authorities, who decide that The Kid needs to be taken to an orphanage. After a fight and an elaborate chase, The Tramp gets The Kid back and the two become fugitives. At the same time, John's mother, still unaware of his identity, comes back to the hospital to ask how the sick little boy is doing. The doctor explains that he is missing and shows her the note The Tramp gave him, which, of course, she recognizes.
On the run, The Tramp and John spend the night in a cheap boarding house, but the manager has seen the posters advertising a reward for any information that leads to the recovery of the missing child, and he takes John to the police station while The Tramp is asleep. When The Tramp wakes up, he panics, unable to find the little boy. He returns home, where the door is locked, and takes a nap outside, dreaming of his neighborhood becoming filled with angels and demons. His sleep is interrupted when the police officer abruptly wakes him, taking him to a mansion where the front door is flung open. The film ends with The Kid and his mother welcoming The Tramp into the house.
