The story begins that summer in which everything changes. Ten-year-old Noah revels in impossible adventures with his faithful imaginary buddies - Mortando Malone, a completely imaginary detective dog, and Big Blue Cat, a giant space creature, and with his real friend Daniel, an even bigger geek than himself. Suddenly, Sarah appears: she runs like a flash, knows secret places in the woods and the perfect spot on the coast to spot dolphins. She doesn't need imaginary friends because she is fantastic herself. Suddenly something happens inside Noah. Overnight he will have to choose between continuing to live in his imaginary world or taking on the greatest journey of all: growing up.