The Missing Season — Gillian French

Whenever another kid goes missing in October, the Pender kids know what is really behind it: a horrific monster out in the marshes they have named the Mumbler.

That's what Clara's new crew tells her when she moves to town: Bree and Sage, who take her under their wing; spirited Trace, who has taken the lead on this year's Halloween prank war; and magnetic Kincaid, whose devil-may-care attitude and air of mystery are impossible for Clara to resist.

Clara doesn't actually believe in the Mumbler. But as Halloween gets closer and tensions build in the town, it's hard to shake the feeling that there really is something dark and dangerous in Pender, lurking in the shadows, waiting to bring the stories to life.