In the nearly ten years since Half Life 2: Episode Two's release, the idea of a sequel - be that Episode Three or Half Life 3 - has turned from an announced certainty to one of gaming's great mysteries.
It seems that Gordon Freeman and Alyx Vance's story ended with Episode Two's cliffhanger. A follow-up was in development, but after numerous problems and the significant passage of time, it turned to vapourware.
The idea of a sequel is now more meme than game, and with each passing year the likelihood of it ever being made dwindles. However, questions as to what happened and what might happen remain in the public consciousness.
Such a question was posed to the Game Informer podcast, which prompted the magazine and website's executive editor Andrew Reiner to drop a tidbit he gathered while investigating the game's development.
"I was actually chasing a story on Half Life 3, trying to figure out what happened. I talked to one developer who actually gave me legitimate information and told me it was a hot mess.There were so many different prototypes that were small teams - 4 or 5 people working on them - that just never got off the ground.
"They said two of the directions they were going in... one was going to be an RTS [real-time strategy] game for Half Life 3 or Episode Three, whatever they were going to call it. The other one involved live actors, and it was going to be a new kind of adventure action game with actual actors... Apparently they were working on these things."
It's a small piece of information, but one that offers a glimpse into how the game was supposed to come together in its early stages, and how open Valve were to new ideas.
Regarding his investigation, Reiner said: "I reached out to ten to fifteen people who worked for the company and they just didn't want to talk about it all."He added that even those who conducted interviews for the game closer to Episode Two's release, were just refusing. "Dead end after dead end after dead end," Reiner said.
Episode Two ended with player-character Gordon Freeman and companion Alyx Vance about to depart to find the Borealis, an Aperture Science research ship that once vanished mysteriously and may hold a key to stopping the game's alien threat. As they're about to leave, the pair and Alyx's father Eli are attacked by slug-like Advisors that kill Eli.
On top of development struggles, the ongoing success of Valve's digital sales platform Steam and enormously popular multiplayer game Dota 2, means the company has little need to develop single player games any more.
While not a conventional or straight-forward follow-up, the two Portal games were set in the same world as Half Life - focusing on goings on in at Aperture Science. The puzzle games reference the Black Mesa research facility which was the setting of the original Half Life, and players also walk through the Borealis's dock.
The wait for Half Life's return continues.