On a chilly fall evening at the prestigious Performing Arts High School of Boston, best friends Tali Carrington and June Danforth go missing after auditioning for a play. They're last seen in grainy, out-of-focus surveillance footage that shows them walking away from the school. Two days later in a town south of Boston, Tali is found disoriented and traumatized by the ocean's edge, while June is pronounced dead at the scene.

Tali's mother, Nell, is so bent on protecting her daughter from further emotional harm that she ignores rumors of her husband's involvement and enlists the help of Cynthia Rawlins, a reunification therapist with personal insight into the riptide that hides below the surface of every unsuspecting family. Meanwhile, Detective Fitz Jameson uncovers a criminal undertow involving the high school's overachieving students, and finally sees an opportunity for personal redemption from a secret that's haunted him for years.

As Nell, Cynthia, and Fitz confront their own contributions to the scandals that beleaguer them, their lives turn out to be more deeply intertwined than they'd ever imagined. In the end, they must decide what lengths they're willing to go to protect the people they love while also saving themselves.