SPOILER WARNING: This article contains major spoilers for "Star City Slayer," the latest episode of Arrow.
In "Star City Slayer," the latest episode of Arrow, the team bid adieu to Curtis "Mr. Terrific" Holt. After he found himself disagreeing with A.R.G.U.S.' suspect methods, he took a job in Washington D.C. and left Star City behind.
When Diggle resurrected the Ghost Protocol, which started out as the Suicide Squad, Curtis took issue with the decision. He found he just could not morally justify the program. As such, he began to look elsewhere for work. Finally, he found a position in Washington D.C. and informed Dig of his plan to take it.
At first, Dig didn't just accept Curtis' resignation. He attempted to persuade Curtis to stay by offering him a new position: head of A.R.G.U.S.' science devision. Curtis entertained the thought for some of the episode, but -- after encountering the Star City Slayer himself -- ultimately stood by his decision to leave.
Before he left for good, Curtis shared a moment with Felicity. He told her he would sign over his half of Helix Dynamics, the tech startup they began last season. This will likely lay the groundwork for Smoak Technology, which is a corporation with its own skyscraper by the time of the flash-forwards.
Echo Kellum's Curtis Holt debuted in "The Candidate," the second episode of Season 4. With his tech know-how, he became fast friends with Felicity. He officially joined Team Arrow as Mr. Terrific in Season 5, though he split off from the main team in Season 6 with Dinah "Black Canary" Drake and Rene Rameriez, aka Wild Dog, during a disagreement with Oliver. He retired from vigilante life after a severe beating from Ricardo "The Dragon" Diaz and began to work with A.R.G.U.S. instead.
"I had a conversation with [then-showrunner] Marc Guggenheim in season 6. It was my idea," Kellum explained in an interview with EntertainmentWeekly. "I have kids — I have a 12-year-old — and it was just starting to feel like I should be back home more."
"What I will say, this isn’t the end of Curtis. I’ll definitely come back as much as they want me back, and visit and guest-star and whatnot. So, it’s not the end of him," he added.
Airing Mondays at 8 pm ET/PT on The CW, Arrow stars Stephen Amell as Oliver Queen, David Ramsey as John Diggle, Emily Bett Rickards as Felicity Smoak, Rick Gonzalez as Wild Dog, Echo Kellum as Mr. Terrific, Juliana Harkavy as Black Canary, Colton Haynes as Arsenal, Kirk Acevedo as Diaz, and Katie Cassidy as Black Siren.