Half-Life writer Marc Laidlaw, who left Valve in 2016, may have just revealed the proposed plot of Half-Life 2: Episode 3 on his personal website. In a post titled “Epistle 3,” Laidlaw presents what appears to be a thinly-veiled summary of Gordon Freeman’s long-missing adventure in the form of correspondence from someone named “Gertrude Fremont.”

“I hope this letter finds you well,” the letter begins. “I can hear your complaint already, ‘Gertie Fremont, we have not heard from you in ages!’ Well, if you care to hear excuses, I have plenty, the greatest of them being I’ve been in other dimensions and whatnot, unable to reach you by the usual means. This was the case until eighteen months ago, when I experienced a critical change in my circumstances, and was redeposited on these shores. In the time since, I have been able to think occasionally about how best to describe the intervening years, my years of silence.”

Laidlaw left Valve about 18 months ago after nearly two decades with the company, and the remaining portions of the letter detail what appear to be Gordon Freeman’s final adventure (bookended with subtle acknowledgement about the situation surrounding Episode 3 and Valve itself).

The story of “Epistle 3” details the journey of Gertrude Fremont and Alex Vaunt to the Antarctic to find the mysterious ship known as the Hyperborea — stand-ins for Gordon Freeman, Alex Vance and the Borealis, the research vessel designed by Aperture Science that was revealed in Half-Life 2: Episode 2. During the adventure, they encounter the Disparate (Combine), Dr. Wanda Bree (a revived Dr. Wallace Breen) and Mrs. X (the G-Man).

Here’s a quick summary of the story:

After the funeral of Eli Vance, Gordon and Alex fly to the Antarctic in search of the Borealis, with members of the Resistance in tow. Gordon and Alex’s plane is shot down, but they manage reach the research vessel, only to discover the Combine have erected a massive base around the Borealis. The Borealis phasing in and out of existence. The Combine are studying it whenever it materializes. Gordon and Alex encounter Dr. Breen, whose consciousness has been implanted into a giant slug-like creature by the Combine. Breen begs the two to end his grotesque existence. The two also rescue Dr. Judith Mossman from a Combine prison and board the Borealis. The ship continues to shift through time and space, and the trio witness the Seven Hour War and travel to alien worlds. Mossman and Alex argue over what to do with the Borealis. Mossman believes the ship should be delivered to the Resistance where it can be studied. Alex wants to destroy it, per her father Eli’s wishes. Alex kills Mossman and arms the Borealis to self-destruct, with the intention of destroying the heart of the Combine’s invasion nexus. The G-Man appears. Alex recognizes him from her childhood and the two depart this reality together, leaving Gordon behind. As the Borealis approaches its target, Gordon sees the Combine world protected by a Dyson sphere and realizes the futility of their attempt. The Vortigaunts appear and once again rescue Gordon from imminent doom, returning him to Earth.

Details in “Epistle 3” appear to line up with leaked and rumored details about Episode 3. Official artwork from the third Half-Life 2 episode (above) appeared to show the Borealis being observed by the Combine. Purportedly leaked concept art from Episode 3 appears to show Gordon and Alex in the Antarctic, standing near a crashed helicopter.

For his part, Laidlaw described the work as “fanfic” on Twitter, calling the story “a genderswapped snapshot of a dream I had many years ago.” He also addressed the mysterious relationship between The G-Man and Alex Vance, saying “I had no fixed ideas about this. Just planting seeds.”

“That is something Valve might still want to develop, flesh out and explain someday,” he said.

You can read the full text of “Epistle 3” at Laidlaw’s website. Or, if you prefer a version with the original Half-Life character names swapped in, someone went to that effort in a post on Pastebin. That version’s embedded below.