When a teenage joyrider crashes a stolen car and ends up in a coma, a routine DNA test reveals a connection to an unsolved murder from twenty-two years before. It's a cold case that should be straightforward. But it's as twisted as the DNA helix itself. Meanwhile, Karen is mired in grief and guilt after the death of her partner. She finds herself irresistibly drawn to another mystery that she has no business investigating, a mystery that has its roots in a terrorist bombing two decades ago. Karen's intuition is telling her something doesn't add up. But is she onto something? Or has she, as her boss has been anticipating, gone too far this time?