Haggis is depressed and no one knows why. A therapist says he needs a father figure, so Nick reluctantly steps into the role. But when Nick starts to enjoy his time with his new monster son, Eddie and the other monsters start to get jealous.

When Eddie teaches the monsters about lying, little does he realise what he has unleashed. What starts out as a tiny fib soon escalates into a series of huge whoppers, and Eddie has to play along with all of them for fear of being found out.