The story follows Kelsey, a teenage girl on a holiday vacation, who begins witnessing the unfolding signs of a serial murderer who drowns their victims in the sea.

The book received negative reviews from critics, but in recent decades has become admired for its original first edition cover, which featured a wavy blue-and-orange aquatic title font and an artistic illustration of a creepy male lifeguard on the beach, popular as an example of nostalgic seapunk aesthetics and retro pop culture art.

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.

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.

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.

He may just kill you” underscores the reality that in these teen horror novels, it’s best to trust no one, whether in suburban babysitting or on an island vacation.

Professional review blog The Devil's Elbow criticized the book's multiple red herring subplots and the sexism in the book's dialogue, as well as the peculiar dynamics of the Tanner Family, including suggested incest and the callousness of Kelsey Tanner's mother when discussing her late husband.

[4] Publishers Weekly agreed with this, stating, "so many red herrings are thrown into this plot that it seems almost logical when the killer turns out to be the one man both Kelsey and readers have been led to trust.