Puss stumbles upon the legendary hidden city of San Lorenzo, and soon finds himself forced to protect it from thieves.

Puss accidentally gives the orphans a magic substance that will ultimately make them explode. The only cure is guarded by a Sphinx who challenges Puss with riddles - and contrary to his own belief, Puss is not good at riddles.

When Toby's ninja brothers try to get him to steal San Lorenzo‘s treasure, he must decide between them and his friendship with Puss.