Right from the start, Paul Doiron jumps into the heart of the mystery of “Hatchet Island,” the 13th installment in his Mike Bowditch series.

College student Evan Levandowski is making a mentally tortured drive up the Maine coast as winter wanes. He has been avoiding responding to insistent emails from Dr. Maeve McLeary, head of the puffin restoration project on remote Baker Island, where he’d interned the previous summer and where McLeary wants him to return. North of Belfast, he imagines that people are following him. Reaching the Penobscot Narrows Bridge, he stops his car mid-span, gets out, climbs the railing and leaps to his death.

Months later, Maine Game Service investigator Mike Bowditch and Stacey Stevens, his on-again, off-again romance, have set out under stormy skies from East Boothbay in kayaks. They’re paddling for Baker Island, where Stacey herself had interned years before. Stacey’s former college roommate, Kendra Ballard is on the island as a researcher and had sent her a dire message. “Some lobstermen who are hassling us are getting more aggressive. Can you please come out here tomorrow with Mike? Make sure he brings his badge and gun.”

As they paddle on this menacing July day, Mike and Stacey hear distant shotgun blasts. A speeding boat powers passes, which they identify as McLeary’s. They pass Ayers Island, which is owned by Clay Markham, a controversial photographer who famously exhibited photos of children posed as corpses.

When they finally reach Baker Island, Hillary Fitzgerald, a strikingly beautiful summer intern, greets them holding a shotgun. Kendra has to persuade her to let the two even step on the island. “We need help, Hillary. You know how desperate the situation is,” she says.

Mike and Stacey learn that two lobstermen have been harassing the women. Also, Kendra confides to her friends that she thinks Maeve is going crazy. At the same time, they learn that the number of nesting puffins on the island has been dropping precipitously as climate change rapidly warms the Gulf of Maine. It’s also rumored that Dr. McLeary requested that part of the gulf be closed to lobstering to protect endangered right whales. The threats had started soon after. If the situation isn’t desperate enough, a major project donor has died, cratering much of the research project’s budget.

Offshore, trouble returns. A silent, seemingly voyeuristic amateur photographer in an idling Chris-Craft offshore is only one of the island’s tormentors. Two lobstermen, who fly the skull and cross bones and a Confederate flag, are there, too, as they are every day to harass another member of the team, Garrett Meadows, who is black. The captain is hugely overweight, while the stern man appears “made entirely of bone and sinew,” Doiron writes. “The lower half of his otherwise handsome face was seamed with red and white scars.”

When word comes that McLeary is due back, Bowditch and Stacey decide she can handle the situation. They depart for nearby Spruce Island for a romantic getaway, their original destination before they got the note from Kendra begging for help. But that night, they are awakened by the sound of gunshot. In a thick fog, they race back to Baker Island. There, they find that Hillary and Kendra have been murdered and Meadows is missing.

Law enforcement officers swarm the island. McLeary shows up in a state of agitation, but as the crowd thins, she disappears. Bowditch spots her loading her backpack with stones. Before he can reach her, she jumps into the sea to her death.

All this action is just the masterful setup for the novel. For the remainder of the book, with assistance from the fiercely independent Stacey, Bowditch probes into what led to the murders and tries to unravel the heart of the darkness that swirls around the cohort of characters.

From one book to the next in the series, Doiron expands his grasp of the craft.

What distinguishes the 13th is Doiron’s willingness to attend to the lengthy setup, the depth of the characters’ psychological entanglement and the darkness that fuels the story. The mystery is testament to the danger of passions and the heinous perversions and the betrayal they can breed.

Frank O Smith is a Maine writer whose novel, “Dream Singer,” was a finalist for the Bellwether Prize. It was also named a Notable Book of the Year in Literary Fiction by Shelf Unbound. Smith can be reached via his website: www.frankosmithstories.com.