Sarah and Aaron are siblings sent to Camp Cold Lake for the summer. Aaron loves the outdoors, but Sarah hates the idea of going to camp. She's also extremely annoying. As soon as she gets to her cabin, she demands that someone switch bunks with her. Apparently she can't handle the idea of sleeping near a window or on a top bunk.
Needless to say, the other kids aren't too thrilled with her. They wind up pulling a few pranks on her. They convince her that someone threw a lit firecracker at her, and when she runs away, they all laugh. They then agree to start over again and instead put a snake in her bed. During a meeting at the first bonfire of the summer, she throws a fit and wanders off by herself because she gets tired of the long list of rules they have to follow.
Sarah winds up finding a bunch of spiders, which she puts in their beds. Turns out the spiders were dangerous and bit the other girls, but she somehow doesn't get in trouble for doing it because it was just harmless fun. One of her roommates is named Jan. Sarah accidentally reveals that Jan has asthma, which is somehow the end of her world.
They get assigned the same canoe one day. Jan violently shakes and tries to tip the canoe over and tells Sarah goodbye. She flips out over how because she has asthma, they won't let her go on some six night hiking trip. Jan then tips the canoe over and takes off, knowing that Sarah isn't strong enough to make it back. Liz, the water counselor, comes out and saves her but then says that Jan told her Sarah tipped the canoe over. They hold a special meeting and make her memorize a new list of camp rules. Sarah decides to enact revenge on the other girl.
Turns out that her idea of revenge is actually to run away. After telling her brother of her plans, she gets stuck swimming. Liz tells her that she can swim on her own, even though they're all supposed to use the buddy system. Sarah dives underwater and stays there as long as she can. She thinks that everyone will think she drowned and suddenly be super nice to her.
When she finally comes up though, she finds that everyone is gone. Running back to the cabins, she discovers that they are all deserted. Even her own things are gone from her cabin. Before she can give up hope, she hears the sound of someone singing. There is also all this snow falling, but through the snow, she can see a girl with long white blond hair wearing a white outfit and singing the camp song. The girl starts talking about how she needs a buddy and wants Sarah to be her buddy. Sarah then realizes that she can see through her, which means that the other girl is dead and so is she.
Della, the blond girl, starts floating above her as Sarah screams. She suddenly wakes up with everyone standing over her. Liz says that she drowned in the lake and stopped breathing but that she gave her CPR. Jan makes a rude comment about how she only did it for attention. A few hours later, she sees Della and starts screaming but there isn't anyone there. Liz thinks she's just hungry and needs to eat.
Later that night, she sees her roommates huddled together and whispering about her. They claim that they just wanted to apologize and start over yet again. They all go out swimming together, but Jan swims ahead and when she turns around, Sarah flips out over it being Della. She passes out and gets pulled out of the water. Sarah then keeps thinking that she sees Della everywhere, and the owner of the camp worries that she camp back too soon.
Since Liz keeps telling her to try new things, she goes water skiing. The driver of the boat turns into Della and comes after her, trying to run her over in the water. Sarah runs back to her cabin, sees her bunk mate Briana, and decides to run away. She gets halfway through the woods before running into Della again.
It turns out that Della made her scared of the lake so she would eventually come into the woods. Years ago, Della died after getting bit by a snake in the woods. Just as she tries to kill Sarah with a snake, Briana comes out of nowhere. The year before, Della did the same thing with Briana. Briana came back to help other girls avoid the same fate.
Sarah and Briana agree to come back year after year and warn other girls, which somehow causes Della to disappear. Briana then reveals that Della actually did kill her the year before and now, she wants Sarah to be her buddy forever. The book ends with Briana coming after her with a snake.
*Sarah is so incredibly whiny that I had a hard time getting through this book. She literally whines and cries at last once in every chapter.
*There is no reason for Aaron to even be in this book. She talks to him maybe three times after they get there.
*Jan is seriously in this book constantly, while Briana only pops up a few times. Having her show up at the end felt like a cheat.