THIRD STRIKE: A Brady Coyne/J.W. Jackson Mystery. By Philip R. Craig and William G. Tapply. Scribner, New York, N.Y. December 2007. 323 pages. $24 in hardcover.

It’s August on Martha’s Vineyard and the union workers at the Steamship Authority are on strike. A hundred thousand people are trapped on the Island with no means of escape, and as desirable as it is to be here, no one cares to be forced to stay; all of a sudden the Vineyard is a plush Alcatraz. Into this stew of fraught feelings, a striker blows himself up with a bomb apparently planned for some other dark purpose.

Veteran detective writers, the late Philip R. Craig and William G. Tapply, have teamed up their talents and their protagonists twice before. Number one was First Light, about greed and Vineyard real estate (that’s far-fetched!); number two, Second Sight, featuring a Courtney Love-type rock star in peril. Now with Third Strike, union problems and a modern Thoreau ex-ballplayer holed up in Menemsha escalate into a terrorist threat to an ex-president.

In each of the Craig/Tapply capers, the stories seem polished and well-organized, as if both writers sat on the floor with dozens of index cards between them, each card representing a different plot-spin: “Why don’t we have the body buried in pig muck show up in this chapter rather than that chapter?”

Instead the creators worked this way: They would agree on a loose story line and, because their joint mysteries take place on the Vineyard, Mr. Craig would write the first chapter starring Island fisherman, ex-cop, family man and part-time sleuth, J.W. Jackson. He would then e-mail the chapter to Mr. Tapply in Hancock, N.H,, who would read it, mull it over, then produce a second chapter featuring Boston attorney/sleuth Brady Coyne, whose case files would yield some quandary dragging him down to the Island. Since J.W. and Brady love to fish, cook, eat, yuk it up, and chase down killers together, their cases invariably mesh to produce one story under a single dust jacket.

Both authors have placed themselves in the detective genre continuum midway between the hard-boiled and the so-called cozy. Requirements for the cozy include lots of lovable locals (check), rural beauty (check) and a fairly unbloodied corpse (semi-check). What you won’t find in a cozy is the protagonist’s bleak view of the human condition, from Raymond Chandler’s “I was the page from yesterday’s calendar crumpled at the bottom of the waste basket” to Robert B. Parker’s “The university president’s office reminded me of the front room of a Victorian whorehouse.”

Both Brady and J.W. are enjoying life too much to be plagued by bitter reflections, but there are moments in Third Strike where it seems as if each of the two investigators is stopping to smell not the roses but the stinkweed. On the verge of a bar fight where J.W. kicks some serious derriere, he tries to “control a little flicker of primeval red madness that was rising in the blackness of my psyche.”

Brady, later on in the action, blends the classic hard-boiled detachment with irony as he muses, “I wondered what destiny in Doyle’s life had decreed that he should end it here in the rain on a scrubby-oak knoll on the southwestern side of Martha’s Vineyard, a failed presidential assassin, killed in the nick of time by a wills-and-estates lawyer from Boston with an Uzi.”

What works particularly well in the Craig/Tapply collaboration is that the two investigators have a chance to bounce their irreverent and probing ideas off one another. In their separate sets of mysteries, they have affection and input from their partners — J.W.’s wife, Zee, and Brady’s girlfriend, Evie — but having each other adds spice to the story (consider other successful detective series duos — Spenser’s Hawk, Doc Ford’s Tomlinson, and Stone Barrington’s Dino: should any of these side-kicks disappear from the scene, readers would go into mourning).

Third Strike marks the final co-authorship, of course, of Phillip R. Craig and William G. Tapply. As everyone knows by now, the former died last May. His latest J.W. mystery, Vineyard Stalker, was released only a couple of weeks after his death, and a final coda will appear in the spring, the 19th in the long-running, enduring series. For those readers coming fresh to Phil’s work, perhaps through Third Strike, they have a full canon ahead of them.