1948: Post-war Britain and an ex-soldier has been found dead with his skull nailed to the floor. Now this case has been re-opened due to media attention and pressure created by his grandson. The killer strikes again and the team discover another linked murder from the 1960s. A further victim is found nailed to the floor - this time in a nursing home for the elderly. Is the Second World War the linking factor? The team must find the next possible victim but no-one knows where he is.