BROKEN HARBOR. By Tana French. Viking. 450 pages. $27.95.

“Let’s get one thing straight: I was the perfect man for this case.”

So begins “Broken Harbor,” the fourth in Tana French’s series of psychological mysteries, all set in a fictional Dublin Murder Squad.

The speaker is Scorcher Kennedy, the detective with the highest solve rate for seven of his 10 years on the squad. Readers who met Kennedy in “Faithful Place” know him as the by-the-book cop who gives grief to that book’s protagonist, the freewheeling Frank McKay.

When Kennedy tells his own story, the emphasis shifts, and French makes us understand why he holds the rule book so dear.

As in each of her novels, French centers on a perfect merger of case and character; in each, a detective stakes everything on a case that only he or she is fit to solve.

The case at hand is a gruesome one: A family of four has been attacked at home in one of the new boom developments that crashed with the Celtic Tiger. The husband, Patrick Spain, and two children are dead; the wife, Jenny Spain, is hanging on.

Kennedy and his rookie partner, Richie Curran, are faced with a situation that seems to violate one of his cardinal rules: The dirty little secret of detection, he tells Curran, is that “most victims went looking for exactly what they got.”

Not so the Spains. They worked hard, were “doing everything right” and kept an immaculate house, with one baffling exception: six or so holes smashed in the walls.

As the case develops, Kennedy and Curran discover themselves to be effective partners, each seeming to fill in what the other lacks. Curran’s empathy and human touch nicely offset Kennedy’s hard-boiled insistence on law and procedure.

French uses their differences to create drama and explore the origins of evil. Curran insists that “bad things just happen,” while Kennedy believes something “feral” is loose in the world, ready to claw its way into the unregulated life, or mind.

For all his rational creed, Kennedy is as prey to wild imaginings and memories as anyone. Among the memories is a childhood trauma, enacted at Broken Harbor, the very site of the Spains’ housing development.

The Spains built a fortress to keep disaster out; Kennedy built a system of rules to contain his mind (“the rule to end all rules: your mind is garbage”). French makes us believe somehow in the gallantry of all parties, each on a lonely, doomed quest for control.

Reviewer Catherine Holmes, an instructor of English at the College of Charleston