November 1992. Scotland is in the grip of its coldest winter in 30 years and the Lake of Menteith in the Trossachs is frozen over. A young man and woman walk across the ice to the historic island of Inchmahome which lies in the middle of the lake. Only the man comes back.
Four months later, as staff prepare the ruined abbey for summer visitors, they discover the remains of the body of a girl, her skull violently crushed. Her identity is unknown.
20 years on, retired detective Alan Narey continues to be haunted by the fact that he and his team weren't able to resolve the crime all those years ago. Determined to relieve her father's torment, DS Rachel Narey, now returns to Lake Menteith and unofficially "reopens" the cold case.
After a series of investigations, Rachel discovers that the one man her father had instinctively suspected of being the killer has died after falling from a stepladder. The Police are not prepared to admit that there is anything more to the accident and Rachel must investigate the link without their help. But when she prepares a dangerous gambit, using a covert email operation to uncover the killer's identity, she puts herself in more danger than she could ever have imagined . . ..