A Darker Magic — Michael Bedard

It began innocently enough with the discovery of an old flyer announcing a long-forgotten magic show held on Saturday, August 8, 1936. But since then, Emily and her teacher, Miss Potts, have been drawn into sinister and frightening shadows from another realm. In a life-and-death struggle, the unlikely pair must overpower the evil that lies waiting at the old railway depot.

But time is running out. Again this year, August 8 falls on a Saturday and Emily''s classmate, Craig Chandler, is in grave danger.
He has befriended a mysterious boy and fallen under the spell of a darker magic.