When Dr Alastair Cameron-Strange meets Alan Bletchley during a hectic shift in the emergency department, he believes he has discovered a violent terrorist threat hidden within an obscure cryptic crossword. Facing ridicule from his peers, Cameron-Strange takes matters into his own hands and embarks on a personal mission which leads him to the far north-west of Scotland and the edge of insanity. It is now a race against time, to tease out the cryptic clues and cut the puzzle short. Everything must click into place.