With one unexpected email from her estranged best friend, Lucy, Mina Murray’s carefully curated life is turned upside down. Leaving behind her psychiatric practice in London, along with her routine and the calm it brings, she returns to the windswept shores of Wales. Faced with everything she’s left behind, she soon discovers that Lucy’s symptoms mirror those of her mysterious patient with amnesia hundreds of miles away.

Roos Beckman has a spirit companion only she can see. Ruth—strange, corpse-like, and dead for centuries—is the light of Roos' life. That is, until the wealthy young widow Agnes Knoop visits one of Roos' backroom seances, and the two strike up a connection.

Thirteen-year-old Ben is sent to a remote reform program for troubled teens by a juvenile court judge. But when he arrives at the camp, located on the edge of the vast wilderness of northwestern Montana, he immediately recognizes that there is something off about the counselors. They’re too friendly and upbeat…yet Ben can tell there’s an undercurrent of menace. As he gets to know the boys in his cabin, he soon discovers that they each have far more going for them than whatever crime landed them there.

Newly-minted child psychologist Mina has little experience. In a field where the first people called are experts, she’s been unable to get her feet wet. Instead, she aimlessly spends her days stuck in the stifling heat wave sweeping across Britain, and anxiously contemplating her upcoming marriage to careful, precise researcher Oscar. The only reprieve from her small, close world is attending the local bereavement group to mourn her brother’s death from years ago. That is, until she meets journalist Sam Hunter at the grief group one day. And he has a proposition for her.

Clem gets a call that is every mother’s worst nightmare. Her nineteen-year-old daughter Erin is unconscious in the hospital after a hiking trip with her friends on the remote Orkney Islands that met a horrifying end, leaving her boyfriend dead and her best friend missing. When Erin wakes, she doesn’t recognize her mother. And she doesn’t answer to her name, but insists she is someone named Nyx.