Moving to the country to live in a stone mansion has all the makings of a nightmare for 14-year-old Cassie Wade. While visiting her future home for the first time, Cassie sees a face peering from an upstairs window, hears a terrifying scream, and shivers at the whispered warnings on a cold, clinging breeze.

Cassie's parents purchase a grand old house on the Kansas prairie, unaware that it includes an unsolved mystery, a dangerous intruder, and an invisible house guest. Cassie is forced to participate in the menacing stranger's search for hidden treasure after he threatens to harm her brother, Ben, if she doesn't cooperate.

The second frightening entity vying for Cassie's attention is Annie, the ghost of a 14-year-old girl who has haunted the house for over a hundred years. After her death, she learned of a family secret. She cannot rest until she finds some answers and a letter promised to her by her dying mother.

Annie's mysterious family history, the tale of her loneliness and heartache, and the danger posed by a desperate man add up to mounting tension and fear as Cassie is torn between the stranger's demands and Annie's requests. Unable to convince her parents of the danger, Cassie turns to her best friend, Jordan. The girls piece together answers, trying to help Annie while courageously thwarting the ominous intruder.