When a bright blue winged tiger appears on his aunt's sofa, Ozzie can tell he's in for an adventure. He's thrilled to follow Tug-a skyger-through a secret door in the basement and into Zoone, the bustling Grand Central Station of the universe, where a thousand doors act as portals to strange and wonderful worlds. But some doors also hide dangers-and when the portal back to Earth explodes behind him, Ozzie gets more adventure than he bargained for....