Dr. Emma Collins and her team are spending their third summer on the island of Little Happy studying the effect of climate change on the great white sharks who come to the nearby nursery every year to give birth. Along with the last two inhabitants of this former fishing village, their peaceful life is disrupted when a "scientific" team led by her ex-boyfriend and marine biologist Richard show up looking for three bull sharks who we soon learn aren't just any bull sharks.

Echo must deal with the regular dramas of high school, in addition to grappling with the murder of her older sister, Zoë. But when Echo receives a diary from Zoë's boyfriend, she begins to untangle the secret life her sister lived.

In this cunning mystery-horror hybrid, college student Ben inherits a curious old mechanical box that churns out voodoo dolls. When a shadowy figure starts using the box to murder Ben's friends, Ben must find the killer.