Danny Boy is a well-trained German shepherd dog that has been in service with the U.S. Marines, but which is now returned to his previous owner, young Jimmy Bailey.

Jimmy's ex-marine friend Joe Cameron tells him to be patient and spend a lot of time with the dog, take it to all the familiar places they used to go to, and play the same games as they used to.

Jimmy vows to pay for the repair, and he and the other boys start vending lemonade in the street to raise the money.

Without scruples, Andrews helps the farmer to steal the dog in the night, and the new "owner" starts abusing Danny Boy to make him obedient.

Meanwhile, Jimmy has found the whip and Danny Boy's leash in the farmer's barn, proving that he had abused the dog extensively.