Are we talking Spenser here? Not yet – we’ll get to his latest title later. For now, consider the exploits of John Cuddy, an ex-army MP turned insurance-company detective turned P.I. Through eight books, Jeremiah Healy, a law professor who writes splendid plot lines, has developed his own version of the lone American hero. Cuddy has battled rogue Vietnamese and their army confederates (“Staked Goat”), rescued a poor black college boy accused of murdering his well-to-do white girlfriend (“So Like Sleep”), even helped the Boston mob track down a killer who was too close to home (“Shallow Graves”).

Now, in _B_Act of God b(344 pages. Pocket Books. $20), he’s hired simultaneously by two people: the widow of a mysteriously murdered furniture-store owner and the brother of the dead man’s secretary (she has turned up missing). As though that weren’t complicated enough, Cuddy also must protect the feelings of the widow. Her husband had survived Buchenwald. He lived an exemplary life. What would Cuddy gain if, in finding the killer, he destroyed the widow’s memories?

For an introduction try last year’s “Foursome,” now in paperback. There Cuddy solves a gruesome triple murder on the shores of a Maine lake, by taking on environmental terrorism, corporate jerkdom and family dysfunction, writ large. As usual, he has memorable side characters: look for Las Hermanas, the all-female gang.

The other steady Boston series is Robert B. Parker’s Spenser tales. His latest, _B_Walking Shadow b(270 pages. Putnam. $19.95), is one of his better recent efforts. It’s not a repeated plot (the misunderstood kid in trouble or the wife with the secret past). It’s a fresh look at a stalker, a Chinese gang and a police chief with a remarkable hold on his little town. Hawk, the fabulous sidekick, returns, bolstered by reformed hood Vinnie Morris. Spenser, who still refers to the time he boxed Jersey Joe Walcott, clearly needs backup. Only one disappointment: no reference to an obscure beer.