When an unidentified flying object is picked up on international radar, the Royal Air Force is dispatched to identify it. But after they goof and accidentally shoot it down over the Scottish highlands, they uncover a terrible secret: Earth is the battleground for a full-scale intergalactic war. Fred Ward, Maggie O'Neill, Phyllis Logan and Vincent Regan co-star in this taut science fiction drama, originally produced for the BBC.