: Your investigation reveals a dark history involving the Ashinaka sanatorium and an underground laboratory. Soviet and Japanese researchers conducted biomedical experiments on terminally ill patients, attempting to create a breed of super-soldiers. The program eventually spiraled out of control, leaving behind monstrosities and chemical waste.

The "Visitation" in the title refers to deadly environmental events, similar to "emissions" in the S.T.A.L.K.E.R. games, which require players to seek immediate shelter. Tunguska: The Visitation - Final Cut on Steam

: As you explore, you discover that a Soviet-funded mining operation was extracting plutonium from the original impact site. This, combined with radioactive waste, mutated the environment, creating "quantum Distortions" and dangerous "Ghouls".