When the murder of a crooked accountant unravels a trail of greed that threatens to expose his identity as legendary assassin, Goliath, Tom and the accountant's widow, Olivia, must keep each other dangerously close. As they try to solve the riddle her husband left behind, and become more and more immersed in the puzzle of each other, Tom and Olivia draw in Tom's fellow officers DS Niamh McGovern, DCS Jackie Twomey and DC "Birdy" Bird, as well as his daughter, Izzy, until deceit and betrayal build to a shattering climax.

本剧为北爱题材，讲述了一辆从斯特兰福特湾中捞起的车中发现了疑似为自杀遗言的纸条，北爱尔兰警探Tom Brannick将其与一桩臭名昭著的悬案联系了起来，而他和这起旧案有诸多关联。这个发现引发了对一名传奇杀手坚持不懈的追捕。