Martin Moone is eleven and completely fed up with being the only boy in a family of girls. He’s desperate for a decent wingman to help him navigate his idiotic life. So when best mate Padraic suggests Martin get an imaginary friend – or ‘IF’ for short – he decides to give it a go.

His first attempt is Loopy Lou, a hyperactive goofball who loves writing rubbish rap songs. But Martin soon gets fed up with Lou’s loopiness and decides to trade in his IF for someone a little less wacky. Enter Sean ‘Caution’ Murphy, an imaginary office clerk in a bad suit with a passion for laziness and a head full of dodgy jokes. Sean is full of tips and tricks to guide Martin through the perils of the playground, from dealing with his sisters’ pranks to beating the bullying Bonner boys. But getting rid of Lou is not that easy, and having TWO imaginary friends is a recipe for trouble!

Martin’s parents are strapped for cash: it’s going to be a budget Christmas this year. So Martin plans to buy his own presents – and attempts, unsuccessfully, to get a job. Padraic puts in a word for him with his Auntie Bridget, who runs the local butcher’s shop. But her shop is struggling as the fish shop across the road undercuts her, and Bridget just can’t compete. No one knows how the owner, Francie Feeley, does it – especially since he doesn’t seem to employ anyone at his fish factory. No one goes in; no one comes out – it’s a mystery.

Intrigued, Martin decides to go undercover and find out the truth, like a fish-mole – or a fish detective. Martin infiltrates the factory and discovers that Francie is illegally employing a gang of Brazilian fish-gutters. They’re a lot of fun and one of them, Fabio, becomes Martin’s good friend. But when Martin is exposed as a spy, he has to choose which side he’s on. Will Christmas be ruined for the whole of Boyle?