Something wicked is lurking on Mt. Tibidabo, something that only comes out on Wednesdays . . .

Every Wednesday, strange things happen in Max's village. The townsfolk shutter their windows, lock their doors and hunker down to outwait this plague of peculiarities referred to simply as "the Wednesdays." But Max is too curious for that, and when he accidentally lets the Wednesdays inside, his furious parents cast him out for the rest of the day.

Soon he meets the Wednesdays themselves; strange silver-eyed boy-creatures bent on spreading mischief and mayhem. Initially he thinks they're quite fun, but they can also be cruel and dangerous. With the assistance of an unlikely cast of characters including a popular girl with questionable motives, a slightly crazed parapsychologist, and the world's ugliest dog, Max must put an end to the curse of the Wednesdays . . . or become one himself.