Upon his arrival, Osmo meets Gustav, a yellow yeti. His distant cousin Rita feels suspicious about the monster's presence, which is prohibited by Winterton's rule book; Osmo and Rita's first family dinner goes awry.

Osmo and Rita's first family dinner party goes horribly wrong and threatens to cut Osmo's stay in Winterton short, but Gustav is there to save tradition at Mayor Chrome's table.

When Osmo has to get a skiing licence or be banished, Gustav becomes his clueless ski instructor and Rita pits him against Mayor Chrome in a downhill race to stay in Winterton.

When monster panic strikes Winterton, Gustav volunteers as a stand-in yeti for Mayor Chrome's monster-preparedness drills, but struggles to be convincingly scary.

Rita finds proof that her heroine, Emma Erton, is the real founder of Winterton, but Anders and his minions get hold of it.

When Osmo's inflatable doughnut goes missing with everyone's mail, the trio search for Winterton's Mail Cats, who have gone feral. The Northern Lights offer help, for a sacrifice.