When snow prevents Mr. Hughes from opening the library one day, book-loving Library Fish finds a way to entertain herself and her bookmobile friend.

Paired together after a veteran detective retires, Platypus Police Squad members Rick Zengo, a hotshot rookie, and Corey O'Malley, a hard-nosed old-timer, struggle with their differences while tackling their first case involving a missing schoolteacher and a duffle bag filled with illegal fish.