Conspiracies was the first published part of the saga in 2005. Conspiracies Deluxe includes part 1 and part 2 of the original saga. As the brother of a STALKER, you set out to find him. He hasn't been heard from for days. So the search for your missing brother begins in the Chernobyl exclusion zone.
The first 2 releases of the saga were really hyped in parts, while other players didn't like them. Due to the new sector principle, which at that time allowed to create very detailed game world, some players apparently didn't like Operation Flashpoint that they already knew. Conspiracies delivered an interesting storyline, an incredibly intense gameplay experience due to the atmosphere of the title, but also tricky situations that the player has to get out of. As already mentioned, it was new that the player had to complete tubular levels. Normally OFP offered a lot of freedom for the player, you can say OFP was also an open-world shooter.
The theme that Conspiracies used was already present in another game: STALKER - Shadow of Chernobyl. At the time Conspiracies was released, there was no comparable scenario on the market. STALKER - Shadow of Chernobyl was released 2 years after Conspiracies. Thus, one can rightly say that the forerunner of this scenario is indeed our OFP modification, Conspiracies.