South Wales, 1957. There's a military base in the Brecon Beacons that has been empty and silent since the end of the war. But something deep beneath the ground has woken up and the military have returned to harness its power. When the Doctor and Martha Jones arrive they discover that not only does this creature not want to work for the British Government, it would really rather go home, thank you very much. Which would be fine - if only it would stop shouting.