A "mesmerizing" (Stephen King) supernatural novel about a sinister mindfulness app with fatal consequences from the New York Times bestselling author of The Chill. In this "taut, creepy techno-chiller" (Paul Tremblay, author of A Head Full of Ghosts), recently laid-off newspaper reporter Nick Bishop takes a humbling job: writing a profile of a new mindfulness app called Clarity.

The app itself seems like a retread of old ideas--relaxing white noise and guided meditations. But then there are the "Sleep Songs." A woman's hauntingly beautiful voice sings a ballad that is anything but soothing--it's disturbing, and more of a warning than a relaxation--but it works. Deep, refreshing sleep follows.

So do the nightmares. Vivid and chilling, they feature a dead woman who calls Nick by name and whispers guidance--or are they threats? And her voice follows him long after the song is done. As the effects of the nightmares begin to permeate his waking life, Nick makes a terrifying discovery: no one involved with Clarity has any interest in his article. Their interest is in him.