Sam Waterston is trading the courtroom for the West Wing. The 85-year-old actor, who spent more than three decades as District Attorney Jack McCoy on "Law & Order", is making his first scripted TV return since leaving that franchise, joining NBC's upcoming political thriller "Line of Fire" as a former president caught in the middle of an assassination conspiracy.

Deadline first reported the casting, with Waterston set to play former President Thomas Barnes opposite Chris Chalk, who will play the sitting commander-in-chief, President Kayana. Campbell Scott is also joining the cast as Terry, a U.S. senator romantically linked to one of the show's leads. The additions round out a series already anchored by Peter Krause as Secret Service agent Mike Hollingsworth and Hope Davis as his wife, Jane — the two halves of a family whose members are scattered across the FBI, the U.S. Marshals, the Secret Service and the Department of Justice.

The show carries an unusually personal pedigree behind the camera. "Line of Fire" counts Jenna Bush Hager among its executive producers, and according to reporting from Parade, the "Today" co-host partly drew on her own childhood growing up surrounded by Secret Service agents as the daughter of President George W. Bush. Joshua Safran and Ben Spector created the series and executive produce alongside Hager.

A homecoming, of sorts

Waterston's casting is being framed by outlets as a full-circle moment for one of network television's most durable leading men. He first played Jack McCoy in 1994, stuck with the role through the original "Law & Order" run's cancellation and 2022 revival, and finally hung up McCoy's suit in February 2024 after more than 400 episodes. At the time, he told The Hollywood Reporter he'd always sensed an expiration date on his comeback.

"The time has come for me to move on and take Jack McCoy with me. There's sadness in leaving, but I'm just too curious about what's next."

That curiosity has now landed him in front of NBC cameras again, this time as a former head of state rather than a prosecutor. "Line of Fire" is set to premiere Monday, September 21, at 10 p.m. ET on NBC, with episodes streaming the next day on Peacock — putting Waterston back in prime time just over a year and a half after his "Law & Order" farewell.

For NBC, loading a freshman thriller with a Law & Order legend, a Bush-family producer and a plot built around a presidential assassination plot is a fairly blunt bid for attention in a crowded fall schedule. Whether it works will depend on whether the Hollingsworth family's cross-agency drama can hold an audience once the novelty of Waterston's return wears off.