Iggy is excited as he sets off with Dad on his first hunting trip. More so when they find a set of footprints too large even for a mammoth. Alongside are a heap of bones and a pool of slime the colour of egg white. Iggy wants to hunt the creature, but Dad is suddenly anxious to get back. Later, Iggy's Grumma tells him about the Slimosaur — a great scaly beast which coats you in slime before devouring you in one go. Many moons ago it terrorised the tribe and a dozen Urk children vanished. 'Nothing to worry about,' she says.
The Urks have had a poor harvest and food is running very low. Chief Hammerhead calls the Elders to discuss solutions to the food shortage. It's decided that to appease the spirits one of their tribe must be sacrificed to the Slimosaur. They cast lots and to Iggy's dismay his friend Umily draws the shortest stick.
Umily is taken to the forest and bound to a stone. She hears rustling noises. Something is coming … Iggy appears! He has come to the rescue! He is armed with a small catapult and a net. Hopefully he has a cunning plan.