It looks like an open-and-shut case: an elderly couple, spooned back-to-front, dead in their bed, an unlabeled vial and a syringe on the night table. Suicide pact, sad but simple.Or not. One of the investigators on the scene is Detective Inspector Tom Thorne of the London Metropolitan Police. Much to the chagrin of the officer in charge of the case, Thorne doesn't think it was a dual suicide. He can't quite put his finger on why — it's not just the unlabeled insulin vial, the absence of a note or the fact that the woman took out her false teeth before dying — but to Thorne that peaceful scene looks like murder.So Thorne starts digging, and soon he turns up several other recent suicides by older people. They died by various methods, but one thread runs through their shocked survivors' reactions: The dead were happy people, aging but reasonably healthy, with no signs of depression or despair. These are murders, Thorne is sure. But they're none of his business.The Dying Hours is British author Mark Billingham's 11th novel about Thorne, a prickly loner who is a relentless investigator, often at the cost of his personal relationships (in the mold of such series characters as Ian Rankin's John Rebus). Billingham, who has been an actor, TV writer and standup comic, began publishing crime novels in 2001 with Sleepyhead, the first Thorne book. (He has also written the Triskellion series of thrillers for kids.) The bestselling Thorne series has twice won the Theakston's Crime Novel of the Year Award and won the Sherlock Award for Best Detective. A television series based on the Thorne novels aired in the United Kingdom in 2010, starring David Morrissey (The Walking Dead) as Thorne.In The Dying Hours, Thorne has been busted down from the murder squad after the events of the 10th novel, Good as Dead. Thorne is chafing at his demotion but enjoying (mostly) his growing relationship with Helen Weeks, the fellow officer he saved from a hostage situation in Good as Dead. The domestic scenes centered on Thorne, Helen and her toddler son are a highlight of The Dying Hours. But at work, Thorne is running up against resistance at every turn; his superiors don't want him investigating homicide cases, period. That just makes him more determined, and soon he's on the trail of a ruthless killer with a clear motive — but because Thorne has had to bend the rules in every direction and beg favors of his friends on the force to construct his case in his spare time, he can't just bring the killer to justice and be done with it. And as Thorne's investigation progresses, it brings him, and those close to him, to the killer's deadly attention.Billingham is fiendishly clever about subverting our expectations, the book's two-page prologue being a bravura example. He's also adept at sketching believable characters very quickly, so that each of the killer's very different victims are real to us, not just corpses after the fact. Thorne's friends and colleagues are even more vivid, like his best friend, Phil Hendricks, a multiply pierced, pub-crawling pathologist and hopeless romantic.But the hunt is what drives The Dying Hours, and it comes to a breathtaking and surprising climax, with the last sharp twist saved for the final pages. Colette Bancroft can be reached at [email protected] or (727) 893-8435.