A race-against-time, twisty thriller set on the stunning—and punishing—lava fields of Iceland, from the bestselling author of Her Last Breath and The Last Word.

Kat and Aaron Mitchell are on the final stretch of a weeklong road trip across Iceland. The journey together, which Kat hoped might heal their marriage, has served only to underscore how far apart they have grown. The space between them feels impassable, colder than the arctic landscape, and seven days of driving in silence hasn’t brought them any closer.

Until they almost run over a teenage girl standing in the middle of a rural highway. She’s appeared seemingly out of nowhere. She wears no jacket, and blood pours down her face.

Kat sees it immediately in the girl’s tear-filled eyes: You’re going to die today. Both of you.

A man, large and threatening, steps out of the evening shadows and into the Mitchells’ rental car’s headlights. The man says he’s the girl’s father. They’ve been in an accident, the man claims, and all they need is a ride to their hotel.

Aaron is wary. But Kat is a physician. She refuses to leave this girl injured in the cold. She helps both strangers into the car, and her husband doesn’t stop her.

She’ll regret that decision for the rest of her life, which may not be very long.

When the horrifying truth about these two passengers comes to light, Kat and Aaron find themselves locked in a race against time with a child’s life on the line. Cut off from civilization, miles into the harsh volcanic tundra, they must outwit a merciless killer.

And Kat comes to realize she can’t trust anyone. Not even her own husband.