As part of the army battling the Jackknife fire in northern California's Lassen Volcanic National Park, Anna, in her capacity as spike camp medic and security officer, tends the injuries and the frayed nerves of the firefighters. When the National Weather Service predicts a cold front followed by snow, promising to all but extinguish the fire, the camp is demobilized, but a last-minute rescue of a firefighter with a broken leg detains Anna and the San Juan crew. Driven on by the erratic thunderstorm of the front, wind shears in the steep canyon, creating the deadly weather conditions for a firestorm. As the ravine explodes in flames propelled by the racing winds, the crew tries desperately to outrun the blaze, ultimately seeking refuge in their individual silver fire shelters wryly referred to as shake 'n' bakes.
When the fire finally passes, Anna emerges from her shelter to check on the fate of her companions. The sound of each exhausted voice, the sight of each bruised and blackened figure, is cause for celebration - until one member of the crew is found inside his shelter with a knife in his back. With darkness comes snow, making immediate rescue impossible, and Anna must tend to the physical and emotional wounds of the crew while seeking the identity of the murderer in their midst.