Major Crimes Season 4 Spoilers

Major Crimes: Who Will Go 'Way Off the Reservation'? Plus: A Sneak Peek

This Monday at 9/8c, TNT’s Major Crimes resumes — again — its fourth season with a “bonus” five-episode arc, in which a particularly tragic double-homicide dovetails with an old case that blew up Tao’s previous partnership, with a detective played by Jason Gedrick (Boomtown).

Previewing the distressing storyline catalyst, series creator James Duff told TVLine, “A woman and her baby are shot to death in an SUV as its gliding through a Latino gang’s territory at 1 am in the morning. When we examine the car, we find heroin under the baby seat, and there is a huge turf war going on between the Bloods and the Diablos for the street trade in heroin. And when we check the [bullet] casings, it points back to a murder committed 12 years ago, where the gun was never found.”

In fact, said years-ago murder was of multiple people — namely, an off-duty LAPD officer and a deputy district attorney — and Tao’s old partner, Mark Hickman (played by Gedrick), “perjured himself on the stand in an attempt to close the case, and was fired,” Duff says. Even when he resurfaces all this time later, the grudge against his former employers is strong. “He feels like he was singled out,” Duff explains. “He feels that everybody perjures themselves, that the police are on the side of good and it doesn’t matter what they say, but that’s not how the LAPD works anymore. It may have worked that way in the late ’80s, early ’90s, mid ’90s, but not anymore.”

But now that the case is being revisited, Hickman sees a chance for possible redemption. “It was the case that ended his career and ruined his life, but now that the gun is back out there and someone is using it, he has a very good case,” says Duff. “It’s an interesting story, and it features Tao (Michael Paul Chan) and Sykes (Kearran Giovanni) in ways we haven’t seen them working before.”

Because while Tao is far from inclined to help his former partner clear his name, Hickman will appeal to Detective Amy Sykes to work with him, on the down low, to follow-up on this possibly exonerating development. Since Hickman “is a bit of a racist,” Duff notes, it’s unlikely partnership, and one that threatens to land Sykes in the crosshairs of Commander Taylor, who has warned the LAPD ranks against allying with the disgraced detective.

“Sykes goes way off the reservation in these five [episodes],” Duff previews. “We sort of set up that she’s capable of doing that last summer. But she does it here in a much bigger way.”

Watch an exclusive Major Crimes sneak peek, in which Hickman defends his 12-year-old testimony to Sykes, during a discreet rendezvous: