A Taste of Smoke — Marion Dane Bauer

Thirteen-year-old Caitlin is looking forward to this camping trip with her older sister. Pam's been away at college all year, and they have a lot to catch up on. But nothing goes the way Caitlin has planned.First, a young man, Alex, shows up at the campsite, and it's obvious Pam has been expecting him. Then Caitlin encounters an oddly dressed boy, Frank, who is almost too eager to befriend her. But Caitlin seems to be the only one who can see and hear him. What exactly does Frank want from her?