Nobody mourns the death of Paul Ramsey when he gets hauled up, snagged on a lobster trap at the end of chapter two in “Beneath the Depth,” Bruce Robert Coffin’s new John Byron mystery. At first, Ramsey is thought to have drowned, probably drunkenly falling off a wharf along Commercial Street in Portland. But when a slug is dug out of his brain, it’s clear the notorious trial lawyer failed to win over more than just a jury on his last day alive.

Portland Police Det. Sgt. John Byron and his partner Det. Diane Joyner are called to take a ride on a fireboat out to the scene shortly after sunrise. The “floater” is identified by ID in his wallet, as one in attendance says, the “big shot attorney” who’s on the front page of the morning Portland Press Herald. The Press Herald story is about his losing a major case for his law firm the day before. A multimillion-dollar judgment hung on the verdict, as did Ramsey’s hope of finally making partner at Newman, Branch & DeWitt, one of Portland’s powerhouse law firms. Suicide? Murder? It was certainly a run of bad luck for Ramsey, whose vanity license plate was “I WIN.”

The problem that detectives Byron and Joyner face is that there is no shortage of people who harbored hard, perhaps lethal, feelings toward the arrogant, obnoxious lawyer. The group includes his most recent client, parents who’d sued the city’s major hospital for malpractice resulting in the death of their son – a couple who Ramsey had talked out of settling with the hospital, adamant that he would win them a huge settlement. There is also a bar patron that a drunken Ramsey had insulted as being stupid. Plus a gay man out with his partner who Ramsey had bumped on the sidewalk after leaving the bar, continuing with his insults. The man took his partner home, then returned to settle the score. Ramsey’s wife, Julie, is on the list of possible suspects, too, a nice enough woman who’d endured years of her husband’s philandering. Not to be overlooked is a young stripper with whom Ramsey had a running tryst. Also his drug dealer. And possibly someone in his law practice.

So many threads pull in so many directions that it is hard for Byron and Joyner to keep them all straight. Compounding things is a young newspaper reporter who seems to have an inside track that enables him to break stories on the murder case, which aggravates Byron and Joyner; their boss, Lt. Martin LeRoyer; and Chief of Police Michael Stanton. The chief wants a tight lid on everything so as not to threaten the cozy relationship he has with Ramsey’s law firm and the big donations it provides to fund the chief’s pet community projects.

Add to these, the simmering aggravation in the partnership between Byron and Joyner, who are lovers, though it is against department policy. It’s stressful enough keeping that a secret from others, which they do badly. They end up keeping secrets from one another, which, again, they do badly. Suspicions and mistrust arise, resulting in the two barely speaking to one another.

Soon enough, suspects and people of interest in the investigation start turning up dead. And then the chief of police publicly announces that the killer has been arrested – who turns out not to be the killer.

Coffin knows the procedural details of police investigations from his days as a former detective for the Portland Police Department. He also knows how to craft a tightly spun tale. The thread that ties everything together is so well buried that the mystery doesn’t begin to make sense until the closing pages. Even then, a couple of grand surprises await.

When the trap is sprung on the killer, it’s the catalyst for the killer to quickly slip the clutches of legal justice. Until this point, Coffin has crafted the story with care. I wish he’d taken a little more time to extend this last major scene, which feels rushed.

It’s a quibble. “Beneath the Depths” is still a great read.

Frank O Smith is a Maine writer whose novel, “Dream Singer,” was named a Notable Book of the Year in Literary Fiction in 2014 by “Shelf Unbound,” an international review magazine. His novel was also a finalist for the Bellwether Prize, created by best-selling novelist Barbara Kingsolver “in support of a literature of social change.” Smith can be reached via his website: frankosmithstories.com