RAF Auchnacluchnie is a nearly abandoned cold-war early-warning radar station situated in the highlands of Scotland overlooking a small village. The two remaining staff Wing-Commander Campbell-Stokes ('Roger Blake') and Airman Tench (Felix Bell) don't seem to realise that the cold war is over and continue to ward off the threat of nuclear attack. All continues peacefully until HQ decide to send Flight Lieutenant Simon Harrison ('Chris Lang') to assess the effectiveness of the station.