U. S. Air Force Interceptor Command Experimental Station No. 6 is a long-range radar installation located in Winthrop, Manitoba, Canada. Unexplained deaths begin to occur in the general area of a farming village near the American base. Postmortems reveal the victims were murdered and the brains and spinal cords are missing from the corpses; the only clue left behind are two puncture marks at the base of each skull. The locals, however, become convinced that radiation leaks from the radar installation's nuclear-power experiments are the cause of the mysterious deaths.