From the #1 New York Times bestselling author of The Mystery of Locked Rooms, when a centuries old crypt key is lost-unleashing a dark force-it's up to the son of the local crypt keeper to end the haunting for good.

"Follow the clues to X Marks the Haunt for a spookily good mystery!"-Alan Gratz, #1 New York Times bestselling author of Heroes

Thanks to his mother's job at a local graveyard, twelve-year-old Will Stone has some unique talents. For one, he knows exactly how a burial vault works and why they're used. For another, he's great at genealogy and can decode centuries old records. Not your normal every day after school activities, that's for sure!

But when a centuries old crypt key is lost, his normally peaceful existence at Graceland cemetery is shattered. Trees wither and die. The lake becomes covered with a sinister green slime that threatens to choke out anything living in it. And suddenly, the graveyard's reputation isn't the only thing in jeopardy . . . Will and his friends' safety is, too.

Suddenly, Will is forced to consider that the lost key might be an even bigger problem than he originally thought. A dark force has been unleashed within the cemetery gates, and along with his friends Stash, Michelle, and Henry, Will must use his unique skill set to figure out which restless spirit is draining the graveyard of life, and how to end the haunting for good.