Newlyweds Mattie and Cole Walker are teaching Cole’s daughters how to snowshoe in a remote canyon when a shattering scream pierces the air. Somewhere ahead, someone has been injured—or worse. Cole takes the girls while Mattie and Robo go deeper into the canyon to find the source of the scream. The investigation that follows uncovers a trail of greed leading to a killer who threatens Mattie’s new family and tests her with the most difficult task she’s faced as a K-9 handler.