Hocus, Fracas, Rumpus and Arena go to the Coliseum to cheer on their uncle Deviatus, Rome's top gladiator. When they realise that a dangerous trap has been set for him, the four children immediately jump into the arena to fight alongside him. The sight of four warlike children causes such a stir that, when they win, the emperor gives them a prize - the island of Cornucopia, where years later they decide to set up an academy for gladiators.