X A # 1 New York Times Bestselling Author A Kinsey Millhone Mystery X: The number ten. An unknown quantity. A mistake. A cross. A kiss... Perhaps her darkest and most chilling novel, Sue Grafton’s X features a remorseless serial killer who leaves no trace of his crimes. Once again breaking the rules and establishing new paths, Grafton wastes little time identifying this sociopath. The test is whether Kinsey Millhone can prove her case against him before she becomes his next victim.