A woman finds the diary of her recently deceased grandfather and reads the chilling story of his time spent in a lighthouse during World War Two. Sergeant Walter Brooke is an expert radio operator in the Second World War and he is sent to the Norfolk coast to a disused lighthouse in order to pick up covert communications from agents in occupied Europe. He thinks he is alone but there is something else there with him and when he turns on his radio, he hears more than just Morse code.