As the novel begins, Dr. Valerie (Valkerie) Jansen is on a field trip on the slope of Mount Trident on the Alaska Peninsula. In real life, this volcano has not erupted for many years—but in the novel, Mount Trident vents sulfur dioxide into the air, and this gas settles into the valley where Valkerie is encamped. She barely survives the experience, at one point taking the air from the tires of her Jeep, which is the only air available for her to breathe.