Valve veteran Jay Pinkerton has left the famed developer.
The writer updated his Facebook page last night with the job news, RPS reported, making him the latest in a string of Valve writers to quit the company.
Pinkerton's writing partner Erik Wolpaw departed Valve back in February - and there was speculation at the time Pinkerton would be leaving as well.
Last month, Half-Life 2 episodes and Portal writer Chet Faliszek also left Valve after a 12-year tenure.
Last year also saw the departure of Half-Life and DOTA 2 writer Marc Laidlaw, too.
Pinkerton's work at Valve encompassed Team Fortress 2's "Meet the..." series and much of Portal 2. Prior to his work at Valve he wrote for Cracked magazine and National Lampoon.
As yet, Pinkerton has not given a reason for the departure. Valve itself has remained characteristically quiet.
Outside of operating Steam, Valve's future as a games developer is opaque. It spoke earlier this year of work on three fully-fledged VR games and recently hired several former members of the Kerbal Space Program team to work on an unspecified project.
Valve currently operates three of the biggest games on Steam: Dota 2, Counter-Strike and Team Fortress 2, but none of those are narrative-focused.