The Tale of the Stalking Shadows is a novella written by David Cody and Bobbi J. G. Weiss. It was ninteenth book in the Are You Afraid of the Dark? book series and was first published in 1998.
Description[]
Rumors about a ghost aren't going to stop Hadley Heering from working at Mrs. Valimon's mansion. The old lady needs a companion, and besides, Hadley is too sensible to believe in ghosts. Luckily, she's also too smart to deny the truth. Because there is something in the mansion--something dark and evil--that only Hadley and the old woman can see, and it's growing stronger every day. Unless Hadley can unlock its terrible secret, this won't be just her first job--it will be her last!