Countdown (1999) was a massive follow-up and expansion on the original Delta Green source book. In it, we learn about similar occult bureaus from the Soviet Union and the UK. But government outfits are only the tip of the factional iceberg. There are criminal organizations, cults (and sometimes criminal organizations that are also cults!), UFO fanatics, tabloid television shows, terror groups and alien invaders.

Despite being based on the literary bedrock of a constantly evolving shared universe, Call of Cthulhu never really had a metaplot (Carl Sandford, the villain from the first CoC campaign Shadows of Yog-Sothoth does turn up in Masks of Nyarlathotep, tho). Perhaps because of the rich fiction it drew from felt like a enough, or maybe because the fatalism so perfectly conveyed in the mechanics made an expansive narrative seem unnecessary — characters just burn up too fast in the friction of the game. Delta Green successfully argues the opposite, that a rich narrative web increases the horror for the players, even if the characters don’t experience the full story. There is a thrill to combing through the histories and time lines, making connections, developing theories. This works particularly well when you discover a reference to something like Masks of Nyarlathotep or another Chaosium-produced 1920s-era scenario — so many artifacts and books that were briefly owned by player investigators once again sit in the storehouses of cultists and madmen. It makes the nightmare world seem somehow more immediate. And because the lore is largely limited to just four books — Delta Green, Countdown, Eyes Only (2007) and Targets of Opportunity (2010) — you avoid the oppressive weight of a constantly expanding metaplot in the vein of Vampire: The Masquerade. Delta Green intrigues and provided endless possibilities, but it doesn’t overstay its welcome.