At America's base at the South Pole, 26 winterovers complete the yearly ritual of waving good-bye to the last plane out, then summon their energies for that season's battle with constant darkness, total isolation and murderous cold that can dip well beneath 100 degrees below zero. Little does the group guess that in succeeding days and weeks, they'll be tested not just by unimagineable weather extremes, but by a murderer intent on gradually eradicating them. Jeff Lewis, as the latest to arrive, becomes the chief suspect when staff members begin to go missing. But he's hardly alone in attracting suspicion. As the death toll mounts and the camp's communication with the outside world is all but extinguished, the fault lines that always lie below the surface of any co-operative effort split open. As hysteria develops and scientific jealousies, romantic entanglements and class bitterness intensify the friction, the polar habitat itself - a football-field-sized dome holding temperatures at tolerable levels - becomes compromised. What's left is a stark choice: root out the psychological contaminant, stop the murderer and the dissent he has sewn, relearn co-operation - or slide down a dark tunnel of everlasting cold.