 A poor boy, who lives with his grandfather after the death of his beloved parents, has only one big friend in his life: his dog Nero. Due to an unfortunate accident, he limps with one leg so he can t play with the other children. One day, when he posts a letter for his grandfather, his dog is stolen by a crook who wants to sell the dog to make a profit. When the dog turns on his kidnapper, the man knocks the dog unconscious and throws it into the river. Three boys come to the rescue and jump in after the dog. They save the dog and fight the crook, who s not happy with these boys. The man eventually tumbles into the water and the boys run off with their new companion: Nero. Meanwhile, Nero s owner cannot be comforted due to the loss of his beloved friend. He has another accident and doesn t regain consciousness. His grandfather, in despair, puts out a reward for the one who returns the dog. The three boys and Nero fight the crook when again, and this time the man loses his trousers and dignity and doesn t return. Nero s owner is reunited with the dog and they all celebrate with a huge cake.