'The Crossing' teams Harry Bosch with his scruffy half-brother Mickey Haller

Relentless LAPD detective Harry Bosch arrived in the early-1990s, taking on complicated cases crafted by his creator, Michael Connelly. Long after Connelly became a brand-name crime writer, he introduced an even scruffier character: Mickey Haller, a defense attorney who blends ambulance-chasing tendencies with bursts of conscientious integrity.

Soon enough, their worlds collided and readers learned Haller and Bosch were half brothers. Other than “The Lincoln Lawyer” in 2005, the first Haller novel, the defense attorney has at least stumbled across Bosch in all five subsequent books Connelly has written about him. (He plays a minor role in another Bosch book.) Connelly also continues to write stand-alone Bosch novels, including “The Black Box” in 2012 and “The Burning Room” last year.

“The Crossing” puts the two popular characters on the same side, trying to prove a reformed gang member innocent of a high-profile murder of a suburban woman in her bed. Haller, defending the accused, persuades Bosch, recently retired from the LAPD, to do some digging on his behalf.

Bosch considers such work professional treachery. Even as he becomes more curious about the crime and who may have committed it if Haller’s client is innocent, Bosch struggles with going to what his former police colleagues consider the dark side: turning into a private eye and helping defense attorneys poke holes in the prosecution.

In characteristic fashion, Bosch agrees to help Haller, but on his terms. Bosch tells Haller he will chase the truth of what happened, but refuses to approach the matter with a bias toward proving the accused innocent.

Here, of course, is where things get more complicated. Despite his prolific output, Connelly rarely stumbles and he continues to find new and interesting angles to explore in detective and legal matters.

This time, a missing Piguet watch, a jewelry store specializing in estate sales, and a plastic surgeon in Beverly Hills are among the disparate pieces in a puzzle that also involves undercover cops.

Connelly never dithers. When he digresses, the journey is often short and sweet. An example from “The Crossing” comes when Bosch daydreams about Vin Scully, the 88-year-old Los Angeles Dodgers announcer who has called big-league games for 66 seasons.

Bosch muses on the fact that Scully has described more than 10,000 baseball games without losing his enthusiasm.

“And [Scully] was always and repeatedly tickled when the vagaries of coincidence produced a running line of twos on the scoreboard,” Connelly writes. “The deuces are wild, he would announce before a pitch. Two balls, two strikes, two out, two on, and two to two in the bottom of the second.”

That said, how does Vin Scully, in Bosch’s mind, relate to crime investigation?

“Bosch could hear Scully’s voice in his head as he considered that the deuces were now wild in his own game. Two murders possibly connected and followed by two brothers killed in the back room of a jewelry store. Two possible killers at the jewelry store. Two car doors heard in the alley where James Allen’s body was left propped against a wall. Two watches said to be stolen and then not. Two vice cops who pull over Mickey Haller on a DUI and two vice cops who may have worked James Allen as an informant. Coincidence? Bosch had a feeling Vin Scully wouldn’t think so, and he didn’t either.”

Among Connelly’s loyal readers, Bosch is his best-known character. Matthew McConaughey made Haller more of a household name playing the lawyer in a movie adaptation of “The Lincoln Lawyer” in 2011. This year, two early Bosch novels became the basis for the debut season of an Amazon series about the LAPD detective. A second season is in production. Maybe a TV-movie crossover is next?

And for Connelly, with “The Crossing,” the chances to keep Haller and Bosch on the same team offer plenty of tantalizing possibilities for him – and his readers – for years to come, no matter what happens on big screens or little ones.