When unexpected debris from outer space crashes onto their peaceful planet, the Clangers explore these strange arrivals with curiosity and wonder. Small and Tiny Clanger stumble upon a leather bag projecting strange noises.

Overcome with curiosity, the Froglets, little orange aliens, join the Clanger children in their investigation of this oddity. They instantly make friends with the musical bag and join in song with him. Tiny and Small invite the bag to dinner, but he rudely eats all the Clangers' blue string pudding! Major Clanger in his anger sends the bag away.

On behalf of the Clangers, Tiny kindly apologises for her family's hurtful behavior. She performs a magic trick for the bag to cheer him up. Tiny magically conjures a lovely jewelled bag from the top hat. Falling in love instantly, the two bags float off in space together to the sound of the Music Trees playing a romantic waltz.