BESTSELLING CLASSIC SERIES! More than 5 million Arthur Adventure books sold! Here's a super-sweet valentine mystery, the perfect treat for every fan of the hit show on PBS Kids. It's almost Valentine's Day, one after another, mysterious valentines addressed to Arthur keep appearing: in his desk, in his lunchbox.... Arthur can't crack the case on who his secret admirer is. Could it be Fern, or maybe even the new girl, Sue Ellen? Or is it just Buster playing pranks? Will Arthur solve the mystery, or will he be left holding a broken heart?