BORDER LINE, by Gerry Boyle, Berkley, 1998; 360 pages, $22.95.

Jack McMorrow, the stubborn one-time New York Times reporter who is like a bulldog when he sniffs out a story, returns in the fifth book about his Maine meanderings by Waterville newspaper columnist Gerry Boyle.

As Maine mystery fans know, McMorrow is going to get himself in trouble with the authorities and any sleazy denizens that populate the backwoods Maine scene he describes so well.

In “Border Line,” Jack has an easy free-lance magazine assignment — a travel piece built around the 18th century trek of Benedict Arnold up the Kennebec to capture Quebec City.

But of course he stumbles on another story — a tourist who disappears from a tour bus in the town of Scanesett Falls. No one else sees the story — especially not the Scanesett Falls police chief, who wants to run Jack out of town.

Jack has time on his hands. His lovely lady, Roxanne, is in Florida trying to get his Alzheimer-wracked mother settled in a nursing home, and his ex-Marine neighbor Clair is visiting his grandchildren in the South.

So he sets out on the Arnold Trail with good intentions but quickly gets sidetracked by the missing tourist — P. Ray Mantis, who debarks a tour bus in Scanesett Falls but doesn’t get back on, and nobody cares. But Jack notices an apparently retarded man, Robie, who lurks around the bus stop and then pedals off.

Of course, Jack finds Robie and his sister, Rob-Ann, who doesn’t seem too bright either, and badgers them about the missing man. He senses that they know something. Two burly “cousins” show up and make life difficult for Jack.

Jack snoops around, gets threatened, attacked, shot at, and then chased by a mysterious truck, but he still persists in trying to find out what happened to the mysterious man with the odd name.

And he is facing a deadline on his magazine article that bogs down the plot. While Jack is digging into the mystery he also travels up the Arnold Trail, and the reader gets a travelogue right along with the action. There is just too much detail about Arnold’s march and the scenery along the route, and it slows the plot down. Then there’s a romantic hook in Quebec when Jack finally gets up there for his story. Does he cheat on the lovely Roxanne? That, too, interrupts the action of the mystery.

But Jack ratchets up the suspense as he discovers apparent CIA ties to the missing man, who appears to have been kidnapped for money. And the kidnappers think Jack is a CIA agent sent to get Mantis, so they demand ransom from him or they’ll knock off the captive.

For a while, there is an attractive, married female cop who does work along with Jack, but then the chief spreads the word that Jack is a deviate, so even red-headed Officer Hope Bell won’t give him the time of day.

What saves the day in this fifth McMorrow mystery is the action and suspense in the plot, plus the intriguing character that is the introspective McMorrow. The descriptions of Maine locale — especially Prosperity, the town whose outskirts he inhabits — add to the reality of the scene.

Prosperity, Boyle writes, “was a sleepy sort of hollow, the town where I lived. The natives ran a few farms, sold vegetables and milk, cut and hauled pulp and firewood. Some of them raised sheep or bees, sold jam and honey. Some sold chunks of land to supplement their Social Security. Mostly they traded news of their children, who had moved far away. The hippies, who landed here 30 years ago, were getting gray, and their children moved away, too.

“In modern times, love of these poor, shadowed hills was not something easily passed from generation to generation.”

We learn a lot about Jack; he’s a “fortyish guy with reddening cheeks, one of which showed a jagged three-inch scar, a souvenir of another story gone sour.” His house is on “the Dump Road.” He drinks tea and ale — but “no ale before five or after seven. It was either that or no ale at all, if I wanted to live long.”

The combination of bulldog Jack and the mystery that others don’t want to see carries this novel along. Skip through the Arnold distraction and the suspense of the missing-man plot is worth the effort.

Bill Roach is a freelance writer with Maine roots who now lives in Florida.