The Fargos are in San Francisco, trying for a little peace and quiet after their not-so-quiet time in the Solomon Islands. Remi has a line on a rare book to buy for Sam, but it turns out to be rarer than they knew, and a wealthy unscrupulous collector wants it as a key to a great treasure. His operatives at first try to scare the couple off, which works about as well as you might expect. The Fargos, unable to resist the lure of a treasure hunt especially when someone doesn't want them on it, pursue clues around the world before a final confrontation in a king's ancient castle.
Since Cussler saves his destroy/take over the world plots for his Dirk Pitt, Kurt Austin and Oregon Files series, the Fargo stories are often quite a bit lighter in tone. Burcell has a better handle on Remi's role and fleshes her out better than earlier collaborators have done. But she is no slouch in keeping the action humming, even though her own novels have leaned more towards procedurals than action thrillers. Some of the seams and joints show, but more outings with the characters will probably smooth them out. Russell Blake had certainly improved on Thomas Perry's lackluster run, but Burcell offers reason to believe that some of the Fargos' better tales are still ahead of them.
Unfortunately, Coleman was working with a character that Parker had not defined all that well, beginning the series just before his late-career doldrums set in, and not giving the Stone novels any boost as he did with his final Spenser books. So while the names of the people and the places were the same as they always had been, they resembled what came from Parker's hand not at all. Coleman added to his problems with a pair of mediocre stories that offered no other reason to enter the town of Paradise, Mass. Debt to Pay, Coleman's third Stone novel, does not solve these problems.
Mr. Peepers, the sadistic sociopathic assassin whom Jesse crossed in Blind Spot, is back to complete his plan for vengeance against those he believes wronged him. Jesse is not the only one on the list, but he's at the top, so when some other targets are found dead, he knows he will have to move to protect his ex-wife Jenn, since Peepers will try to get to Jesse through her. But Jenn is getting married in Dallas, and Jesse is in a serious stage of his relationship with Diana Evans. So moving to protect Jenn will be harder on him personally than he thought. Paradise patrolman Luther Simpson is also in danger, since he shot Peepers to save Jesse. With his attention divided between Dallas and Paradise and Jenn and Diane, Jesse may not be on top of his game, even though he will have to be in order to stop a possible bloodbath.
Coleman makes a number of mistakes -- he takes Jesse out of Paradise for much of the book, even though all of Parker's characters were creatures of their respective places more than anything else. They are much weaker in other locales. He makes the back-and-forth between Dallas and Paradise as confusing as possible. There's a scene in which Jesse and Jenn's new husband are in a bar fight with the ex-husband of the new husband's ex-lover that makes as much sense as it sounds like it would. Mr. Peepers abducts and terrorizes a young woman supposedly as a part of his plot but her role makes no sense. He develops his plans based on a supposed connection with Jenn that Coleman never clearly outlines.
Coleman is free and easy with Parker's characters, perhaps figuring on generating some interest based on George Martin's "Anyone can die at any time" schtick, but it's a flashy wax job on a rusty clunker. The main response Debt to Pay evokes from a reader is a strong desire to seek out Michael Brandman and apologize to him for criticizing what he did to the good and not-so-good folk of Paradise, Mass. Turns out he wasn't the worst thing to happen to them after all.