School at the zoo? Totally wild! The Baby-sitters can't wait to start on their animal observation projects for science class--because they get to work at the Bedford Zoo! But on their very first visit, Mary Anne and her friends smell trouble. Somebody's letting animals out of their cages. So far, each one has been caught and returned without incident. But what if this monkey business turns serious? Can the Baby-sitters figure out who's behind it all, before somebody gets hurt?