Gumball has his sights on one thing: getting the new limited-edition action figure of video game hero Knife Fightgood...except the package turns up missing when he sleeps through the delivery. Knowing the worst has happened--that someone's stolen Knife Fightgood--it's up to Gumball and Darwin to find him! Along with Anais, the boys set off through town following the clues to a mysterious underground system beneath Elmore and uncover a truth they never thought possible.