Shaded with elements of the gothic, McTiernan's novel set in Galway introduces Garda Cormac Reilly. On a cold winter's night in 1993, Cormac arrives at an isolated, crumbling-down Georgian manor called the Dower House on the far west coast of Ireland. There's a muttered instruction; a minor domestic. The woman, Hilaria Blake, has skeletal arms and legs; there are track marks on her arms, so the cause of death seems obvious. Both her children--fifteen-year-old Maude and her younger brother, five-year-old Jack--are neglected. Jack even has some bruises. Cormac wonders how the two children could be left to rot in a freezing, empty house with someone as far gone as their mother. Maude Blake is eventually labeled a runaway, with no family to notice or care that she vanished.
In 2013, renowned heart-surgeon Aisling desperately needs to talk to her partner, Jack. She refuses to sacrifice her future for what was nothing more than a "scrap of biological material, cells dividing, inside her." Twenty years after Hilaria Blake's death, Cormac finds himself at odds with his law enforcement officers Danny McIntyre and Anthony Healy--especially Healy, who thinks Cormac ignored the events that took place at the Dower House. Forced to work solo, Cormac recognizes that he's no longer the golden boy of the Special Detectives unit, the anti-terrorist section. He has a new job working cold cases with a new boss and a new set of colleagues. Resources are limited, and there seems to be an agenda within the gardai. Cormac is assigned to learn more about what happened to Maude Blake. An experienced detective, Cormac realizes something worse than the obvious was going on at the Dower house all those years ago.
Jack Blake's death is ultimately ruled a suicide. Aisling, however, doesn't believe that her lover would take his own life. Feeling disconnected, she ensconces herself in her cold house, in a bedroom with all of Jack's clothes in the wardrobe. Then Maude returns to Galway from Australia. Aisling tells her that Jack wasn't depressed. Jack didn't have any enemies; he was just an ordinary guy. Suddenly Aisling is following a thread, as well as dark-eyed Maude, who urges Aisling to contact the gardai "for peace of mind."
Filled with multiple plot threads, The Ruin builds on Cormac's relationship with his girlfriend, Emma, which started under difficult circumstances; the fallout from Cormac's transfer off the special detectives unit; the Mill Station politics; the tension between moody Danny and DCI Healy; and Danny's missing sister, Lorna, who was reportedly "living it up" at some music festival. A compelling sublot involves a 15-year-old girl who disappeared in 1975. By 1977, she was declared "missing presumed dead." Like the addled plot-line of a dream, the encounters pile up, proving that Aisling may be wrong about Jack, especially when Maude is taken in for formal questioning, the first but unlikely suspect in Jack's presumed murder.
Cormac decides to attack the Blake case with gusto. Hilaria had been abusing alcohol for years. When she came to Kilmore, she attacked drink with "complete singlemindedness." Cormac has tried hard to continue working on the case, yet the more time he spends on it, the more he's convinced there are more questions than answers and a story he hadn't heard: "The night Hilaria Blake died, I was wet behind the ears, first week on the job. I found Maude, found Jack, in a house with no electricity, damp everywhere, the place basically rotting around them." Meanwhile, Danny's sister has been missing for nearly two weeks. Maude might be the one person who can provide some answers as well as Blake's original neighbor, Domenica Keane, a religious fanatic who is still alive. She tells Cormac about a prayer group that originally visited the Blake home.
Family ghosts, local politics and the soul of a country (abortion rights are a theme of the novel) struggle for prominence in a thriller taut with police corruption and the mistakes of Hilaria Blake's past. Jack's death proves illusory to the last. Stonewalled by the police and filled with an anger that slowly burns through "the fog of grief," Aisling finally learns about how a five-year-old boy was abandoned to strangers. Now her lovely Jack is dead by suicide or murdered because of some secret life he had never shared with her. Are Maude's actions simply the work of someone who loved her brother, albeit from a distance of years and kilometers? Maude believes that Jack was killed. Like Aisling, she desperately wants justice. McTiernan notches up the tension with a hostage scene in which Cormac makes a split-second, life-and-death decision. Aisling is ultimately vindicated, though violently, and Danny proves to be knee-deep in the Maude Blake case, pushing it along behind the scenes from the beginning.
I sensed relief, a twinge of emptiness in Cormac's journey and then victory as he finally sees the investigation of Jack and Hilaria Blake as a giant puzzle, every piece fitting together, interlocking with a single gaping hole. Wrapping her murder mystery up with gusto, McTiernan leaves us slavering for the next volume in her exciting series.