Night of the Mask (Frightville #4)

Welcome to Frightville... one-stop shopping for all your fears! Ben has just been invited to the birthday party of the year. The only catch is that you have to come in costume. Luckily, Ben knows just the place to buy the perfect mask -- that cool new store Frightville. It sells all sorts of spooky and one-of-a-kind items. But when Ben puts on the mask he finds at Frightville, suddenly he has the ability to see strange and ominous creatures lurking all around him. Is it his imagination, or are they real?