With only so many books to read and games to play, nine-year-old Henry is certain his stay with his grandpa is going to be boring. But when the storm confining him to the house lightens, Henry's spirits do also, and he sets out to explore the forest behind the house.
Henry ventures deep into the woods. Beyond the enormous oak he never dared pass, he finds a very old, very run-down, and very closed zoo—at least it seems to be those things until the mysterious gypsy caretaker, Ms. Twingle, says there are children inside.
Henry jumps at the chance to play with the other kids. But it doesn't take him long to discover he has made a horrible mistake. The zoo is not what it seems, and neither is Ms. Twingle. Cursed to spend his days as a beast and his nights as a boy, Henry knows if he can't escape, he will be forever Trapped in Twingle's Twilight Zoo, never to see his grandpa again.