When a teenage joyrider crashes a stolen car and ends up in a coma, a routine DNA test could be the key to unlocking the mystery of a twenty-year-old murder inquiry.

Detective Chief Inspector Karen Pirie is an expert at solving the unsolvable. With each cold case closed, justice is served. So, finding the answer should be straightforward, but it's as twisted as the DNA helix itself.

Meanwhile Karen finds herself irresistibly drawn to another case, one that she has no business investigating. And as she pieces together decades-old evidence, Karen discovers the most dangerous kinds of secrets. Secrets that someone is willing to kill for.