Scamp, the son of Lady and Tramp, is bored of life as a house dog after being put on a chain after messing up the house and a heavy telling off from his father. He runs away, and finds a group of strays named 'The Junkyard Dogs'. Scamp wants to join, but the leader, Buster, gives Scamp a test to prove his courage. Scamp had to steal a tin can from a ferocious dog named Reggie, and he succeeded, with Reggie getting caught by the dog-catcher. Buster is impressed.
The group head to the park, where Scamp discovers his father was once a Junkyard Dog. Scamp is impressed, but also careful not to let the others know as they (under the strong influence of Buster) all hate Tramp for becoming a house-dog. Tramp thinks he was too harsh on Scamp, and it is then that the family begin to look for him.
Scamp starts to fall in love with Angel, a pomeranian and one of the Junkyard Dogs. However Angel is angry he would leave his loving family to be a Junkyard Dog, as she had a family once and wants to have one again.
Buster begins to realise Scamp is Tramp's son. He makes Scamp steal from the picnic of his family. Tramp finds Scamp and confronts him about his decision. Scamp becomes a Junkyard Dog, and as a sign of this, he takes off his collar.
Buster still wants revenge on Tramp, so sets a trap for Scamp, which ends in him being caught by the dog-catcher. Tramp saves him from the dog pound, and they all go home.
Buster gets trapped by piles of junk dropping onto him, and all the Junkyard Dogs refuse to help him. Angel becomes part of Scamp's family.