Check out my guide about finding every note easy and fast.

So, it's time for the conspiracy theories. What do we have to begin with? There are 36 notes in the game plus monologues in certain areas of the map. The notes are grouped as follows (9 notes per group):

• logbook - this is actually a diary kept by an investigator who is working in some research facility and was sent to search for the missing hikers. He finds their bodies and then goes crazy in the forest. Two more notes in the logbook have different handwriting and are voiced by a different person. These belong to someone who is kept as a test subject for some experiments. These notes must be collected to complete the game; all the others are optional,
  
• diary - this is kept by one of the hikers. They set off on a journey, and then something weird happens in the forest. In the end, someone tries to get in their tent, and they run away. The diary ends here (the last page just says "Where is Anton? 2/2/1959"),
  
• reports - these are documents and correspondence regarding the above-mentioned facility. They mention various anomalies, using test subjects, and one of them says the investigator has gone missing,
  
• articles - these are, well, articles and press-clippings where anomalies or the facility are mentioned in any way.

Interestingly enough, a person named Anton is mentioned in all the groups. Even the last item in the diary says "Where is Anton?"... and the handwriting is different... different from the logbook, too... they knew Anton in the facility... in the secret ending, Anton is voiced by Sean Bean... as well as the investigator... and the narrator... but in the Polish version, those are different voices... Anton spoke to everyone, but who has really seen him? Seversk, section 22, Vladimir-30... "one alive is not enough..." Anton was in the Death Valley... chamber 7 in section 22... the diary is useless... lights, fog... Anton...

I GOT IT!!!

A scientist named Anton (article 6) went to explore the Death Valley somewhere in Siberia, where mysterious constructions are buried in the ground. There, he gets captured by the orange fog and is turned into a ghost. Anyone who mentioned Anton did not see him alive.

A research unit was created in Seversk to study natural phenomena (report 1). After observing several anomalies, they decided to use prisoners for tests (report 3). Some of the prisoners died, and those who turned out to be useless were eliminated by the unit workers (report 6). At the same time, a lab was constructed in Vladimir-30, where bodies were transported and revival attempts were performed (article 5).

During the research of the anomalies, Anton's ghost entered the facility and talked to some of the scientists and prisoners. One of the prisoners, called Subject 73, after enduring multiple tests, including revival (logbook 9), was reborn and gained supernatural abilities (report 4 mentions one of the subjects could have survived, and article 5 says one "alive" is not enough). He went on the rampage (reports 7, 8) and broke free.

Anton told him that he had to avenge himself and his wife, who did not survive the tests. Engulfed by his desire for revenge, he slaughtered the hikers who happened to be in the area, intending to lure someone from the unit. The unit indeed sent an agent named Vitaliy, who found the hikers' bodies and later, apparently, was also captured by the orange fog.

Doing what Anton told him to do, Vitaliy mutilated his fiancee Vera (article 7) and ended up in a mental institute (logbook 8). The unit, however, disregards the event. Anton, being temporarily left without accomplices (Subject 73 lost his human appearance and could not enter the city), decided to act alone and killed Vera's sister (article 8). The police questioned Vitaliy but could not obtain any useful information. He only mentioned the notes he left in the forest (described in the Aftermath comic book).

The inexplicable murder without any trace of breaking into the apartment has once again drawn the unit's attention. A new agent is sent to search for the notes (the game protagonist). Subject 73 is waiting for him there. Occasionally, he speaks to him, telling him about everything he has gone through (the narrator). The agent manages to collect the notes, but the anomaly in the mountains engulfs him... His fate is unclear.