The Lifeguard (novel)

Kelsey Tanner, a young girl who recently grieved the death of her biological father, is given a summer vacation trip to Beverly Island (fictional location) with her mother and her mother's boyfriend, Eric, who has several children roughly Kelsey's age. Upon arriving on the island, Kelsey and her mother are informed by a horrified Eric that his only daughter, Beth, is missing. A search party has been called in to look for the girl after her belongings are found on the beach; meanwhile Kelsey befriends the other teenagers on the island, including Donna, a preppy girl, and Skip, a wealthy and vain boy who works as a lifeguard. Kelsey is put off by Neale, Eric's son and Beth's brother; Neale is cold, aloof and bitter, and Kelsey doesn't trust him.

It is decided by the search party later on that Beth must have drowned while swimming on the beach, although no corpse is ever recovered. Kelsey finds a note hidden in Beth's bedroom that says "I think someone is going to kill me". Kelsey begins to suspect that Beth was murdered, but is hesitant to tell her peers. She fears for her own life after she hears someone in her bedroom while she's alone in Eric's house, and later when she's about to leave the shower; she hears bizarre noises and notices wet footprints on the floor of the shower room, along with seaweed from the beach. Kelsey discovers a deceased body, but when she alerts her peers to it, the body has disappeared, leading the other teens to doubt Kelsey's sincerity. A creepy old man with an eyepatch, Isaac (a resident of Beverly Island off-season), keeps yelling warnings at Kelsey, terrifying her into thinking that he's some kind of a pervert who may have attacked and killed Beth. Kelsey develops romantic feelings for Justin, Eric's shy younger son and the brother of Neale and Beth, although she is also drawn to Neale despite his cold nature. Kelsey breaks into Isaac's houseboat and discovers items belonging to Beth, but before she can gather any of this evidence, a rat startles her and she flees the houseboat. She discovers that Justin left the note in Beth's room and that he has been listening to her telephone conversations. She also finds Isaac’s dead body in the road; as she comes to learn that a series of drownings have occurred on Beverly Island within the same period, Kelsey suspects that Justin is the culprit, along with Donna agreeing to this, though nobody believes the two girls. When it is verified that Justin is the killer, he attempts to attack Kelsey, but she is saved by Neale; she kisses Neale passionately, and the two teens begin a romantic relationship together although Kelsey is aware that Neale will probably soon be her stepbrother if her mother marries Eric, making them an incestuous couple, though not by blood. Kelsey discovers while in the hospital that Beth and Donna are both alive and safe, but that Justin is responsible for the other murders that have occurred around the island. She wonders what will happen in the future now that the truth has come out.