EXCLUSIVE: The Dexter Trinity Killer prequel series, following the makings of the notorious serial killer played by John Lithgow in the mothership series, remains “in development” at Paramount+ with Showtime and has come a long way since it was originally announced in early 2023 as being in the exploration stages, sources close to production tell Deadline.

Original Dexter showrunner Clyde Phillips and fellow Dexter veteran Scott Reynolds serve as co-creators and executive producers of the Trinity Killer spinoff prequel, we hear. They held a development room for the project earlier this spring. As scripts were being written, there were erroneous media reports that the project was not moving forward which was never the case, sources said.

Phillips shared an update on the Trinity Killer offshoot with Deadline while promoting Dexter: Original Sin in New York City earlier this month.

“We wrote the entire Trinity Killer series. At the moment, it is on the back burner,” he said in the video, which you can watch below. “John Lithgow has agreed to be the voice of his younger self the way Michael Hall is doing for [Original Sin]. There’s that and we’re doing another show with Michael C. Hall, [Resurrection]… We were writing that while shooting Original Sin, so that’s fairly busy. We begin shooting [Resurrection] in January and it will air in June 2025.”

Showtime and Phillips’ focus has been on Original Sin, which premiered Dec. 13, with Resurrection, the continuation of the highly-rated limited series Dexter: New Blood, also as top priority. Resurrection, which will be narrated by Patrick Gibson who plays Young Dexter in Original Sin, was soft-launched in the Original Sin premiere which revealed Dexter survived the shooting that was meant to kill him for good by his son Harrison (Jack Alcott) at Dexter’s request.

The network and studio executives are also likely waiting to see how Original Sin does to gauge if there is appetite for a further Dexter universe expansion before committing to Trinity. So far, things are looking promising as the series premiere of Dexter: Original Sin racked up 2.1M global viewers across Paramount+ and Showtime in the first three days of availability, according to Paramount Global. The company also says it is Showtime’s most-streamed premiere ever, although it didn’t specify how much of that audience came from streaming.

While Dexter was based on the books by Jeff Lindsay, the TV series’ Phillips created the character of Arthur Mitchell aka the Trinity Killer who first appeared in Season 4 of the Showtime hit. Trinity is considered the most infamous serial killer Dexter (Michael C. Hall) has ever slayed. He caused Dexter the most anguish of any of his kills by murdering his pure-of-heart wife Rita (Julie Benz) who he found lifeless in their bathtub in the Season 4 finale. Dexter’s life was never the same.

Some of Arthur’s backstory, which would be explored in the potential prequel, was revealed on Dexter. As a child, he accidentally caused the death of his sister Vera who was startled to see her brother watching her shower and fell through the shower’s glass door. The incident, which Arthur’s parents blamed on him, devastated the family. His mother committed suicide a couple of years later and his dad became an alcoholic who beat Arthur severely. In all his kills, Trinity was inspired by his early life in some way. He bookended his murder spree with the murders of two women in a bathtub, including Rita, his final kill before Dexter hunted him down.

Like Original Sin has done for Dexter, a Trinity Killer prequel could humanize him and explain how he got to the point of no return, not as an excuse but more so as a dramatic take on a psychological profile of why killers kill.

Lithgow returned as the Trinity Killer in New Blood albeit for a bitty part leaving fans hungry for more. Could Resurrection see his return and serve as a lead into this prequel series much like New Blood bled into Original Sin?

New episodes of Original Sin, which is not a limited series and could continue beyond Season 1, air on Friday nights at 10 p.m. on Paramount+ with Showtime, the season finale set for Valentine’s Day.