”The Humans,” by Matt Haig (Simon & Schuster)

Detectives are in short supply among this year’s Edgar Award finalists for best novel. The nominees investigate morality as much as crime, with only two procedurals among the lot. In the others, a small-town professor, a Midwestern preacher’s son, a blue-collar neighborhood in Detroit and an alien all learn, in the words of the awards’ namesake, Edgar Allan Poe, that “the scariest monsters are the ones who lurk within our souls.” The Mystery Writers of America will present the winner in this category, and in several others, May 1 at a gala in New York.

How the Light Gets In , by Louise Penny (Minotaur, $25.99)

Louise Penny’s magnificent mystery was named one of The Washington Post’s Top 10 Books of 2013. The title comes from a Leonard Cohen song: “There is a crack in everything/ That’s how the light gets in.” In his ninth outing, Chief Inspector Armand Gamache of the Sûrté du Québec is left wondering if he can repair all the cracks. He’s facing off against the cunning, amoral Chief Superintendent Francoeur, who suborned Gamache’s lieutenant, Jean-Guy Beauvoir at the end of “The Beautiful Mystery” (2012). The murder of an old woman, the last member of a tragic family of sisters, and the apparent suicide of a government worker lead to a showdown in a small village. “There’s an epic conspiracy at the center of this tale — a battle between the forces of good and evil — the likes of which hasn’t been seen since the heavenly army faced off with Lucifer’s fallen angels in ‘Paradise Lost,’ ” Maureen Corrigan wrote last year in The Post.

The Humans , by Matt Haig (Simon & Schuster, $25)

Cambridge mathematician Andrew Martin spends eight years solving the Riemann hypothesis — at which point he is abducted and killed by aliens concerned that such a quantum leap forward in understanding would allow humans to muck up the universe. (Still with me?) An alien “replacement” is sent to impersonate Andrew and eliminate his wife, teenage son and anyone else he might have told about his breakthrough. In his (its?) first minutes on Earth, the ersatz Dr. Martin manages to get hit by a car and locked up in a psych ward. But he doesn’t seriously botch the mission until he starts caring for the bizarre creatures he’s meant to destroy. Haig’s funny, heartfelt novel is written from the point of view of the baffled interloper as he tries to puzzle out what it really means to be human.

Ordinary Grace , by William Kent Krueger (Atria, $24.99)

It’s the summer of 1961, and 13-year-old Frank Drum and his younger brother have to grow up quickly when their small town in Minnesota is altered by a series of deaths, starting with a young boy hit by a train. As tragedies mount, Frank’s father, a soldier-turned-preacher, desperately seeks grace, while his beautiful mother won’t settle for less than revenge. Written from Frank’s perspective 40 years later, Krueger’s elegy for innocence is a deeply memorable tale.

Sandrine’s Case , by Thomas H. Cook (Mysterious Press, $24)

Professor Samuel Madison always felt superior to the small college town in which he and his wife, Sandrine, ended up — until police arrested him for her murder. As damning revelations pile up in the courtroom, Madison watches with growing horror as he becomes convinced that his brilliant wife is orchestrating events from beyond the grave. While at times it seems as if the Edgar Award-winning Cook is entering “Presumed Innocent” territory, he has a deeper game in mind. “Sandrine’s Case” is undeniably clever, but the case’s resolution is likely to leave female readers cold.

Standing in Another Man’s Grave , by Ian Rankin (Reagan Arthur, $25.99)

The Edgar Award-winner brings back his most famous creation: the hard-drinking, authority-loathing, artery-clogged John Rebus, who abruptly retired from the Edinburgh police force in “Exit Music” (2008). Rebus always was an unlikely candidate as a pensioner — one could imagine him digging in a garden only if he were looking for dropped cigarettes. Now a civilian who combs through cold cases, Rebus is asked by a woman to look into the disappearance of her daughter, who’s been missing since 1999. Ominously, two other girls have disappeared along the same remote stretch of a Scottish road. Calling Rebus’s return “readable, but not without flaw,” Patrick Anderson wrote in The Washington Post last year that “it’s enough to say that it’s good to have the old reprobate back one more time.”

Until She Comes Home , by Lori Roy (Dutton, $26.95)

In 1958, Detroit’s Alder Ave. is governed by a strict set of rules, even as the city’s economic decay starts lapping at the edges of the street. But after a teenage girl disappears on her way home from a neighbor’s house, violence flows in and disrupts life on Alder Ave. Edgar Award-winner Roy focuses on the homes of three women: Grace, a blond beauty who is expecting her first child; Julia, her best friend, whose twin nieces are spending the summer in Detroit; and Malina, whose iron control over herself and her female neighbors grows ever more brittle as the first signs of rust begin to stain this once-genteel immigrant street.

Zipp regularly reviews books for The Washington Post and the Christian Science Monitor.