Patrick and Jenny Spain and their two young children - Emma and Jack - living in an unfinished, decaying housing development in Brianstown (formerly Broken Harbour) Ireland are attacked. Patrick and the children are dead and Jenny is barely alive. Mike ("Scorcher") Kennedy and his rookie partner Richie Curran are assigned the case.
As usual with Tana French's books one of the detectives (in this case Scorcher Kennedy) has an unfortunate history with the murder locale. When Scorcher was a child his family spent summer vacations at Broken Harbour and it was there that his mother committed suicide. Moreover, the tragedy apparently triggered mental illness in Scorcher's sister Dina, who has episodes of paranoia and erratic behavior.
When Scorcher and Richie begin to investigate the Spain calamity Patrick emerges as an early likely suspect. The recession has led to the loss of his high-paying job and the formerly happy family has been experiencing severe money problems. The Spains have had to give up their SUV, their friends, their social life, their recreational activities, and a good part of their self-respect. Maybe Patrick wanted to end all the suffering? However, further investigation reveals that the Spains seem to have attracted a couple of stalkers: one human and one elusive animal that ostensibly crawls through their house at will.
Questioning Jenny, the Spains' relatives, and their rather unsavory neighbors provides a number of clues to the crimes as does information gleaned from the Spains incompletely erased computer files. Scorcher and Richie don't agree about who the prime suspect should be, which leads to some friction between them. However the two detectives seem to work well together and Scorcher thinks about a possibly enduring partnership. And - at least for this case - Scorcher can use the help. His sister Dina, seeing the name "Broken Harbor" in the news has had a break-down and Scorcher is compelled to take care of her.
I don't want to give away spoilers so I'll just say that this well-written story has compelling characters and interesting twists, all of which lead to a satisfying, believable conclusion. A great addition to Tana French's mystery series.