Osmo meets the yellow yeti Gustav after his arrival, while his distant cousin Rita immediately suspects that a monster is afoot. Gustav plays chef for Osmo and Rita's family dinner.

Osmo must have his ski bracelet, so he won't be kicked out of the city. Gustav becomes his monitor. Later, when Winterton panics, Gustav signs up for the defence exercises.

Rita finds proof that her heroine, Emma Erton, is the real founder of Winterton, but Anders and his minions get hold of it. Later, Osmo and Rita suspect Gustav of having gone into monster mode. They isolate him to cure him.

When Gustav takes Chrome's new carpet for his Grandpa, the children help him escort the relic to the monster graveyard. Later, Osmo's donut buoy disappears with the rest of the mail.

Gustav likes a monster that eats people. Osmo tries to join in, but it goes wrong.

Osmo's clone from Monster Mountain runs amok in town. Osmo must prove that his dad is a plumbing hero.