The Ghost of Camp Whispering Pines — Susan Korman

Alison, Heather, Keisha, Megan and Rose arrive at Camp Whispering Pines just in time to join everyone around the campfire. As the campers eat marshmallows, Rachel tells the true story about the founder's grandson, Jacob, who disappeared in a storm and now haunts the premises.

The next day, on a scavenger hunt, the girls lose their way just as a storm is starting. They take shelter in a cave and discover a lost boy named Jacob, but he can't be the same Jacob, can he?

Ghosts don't really exist--do they?