In 1975, an abnormal phenomenon emerged in a forest in eastern Poland. Trees at the forest's edge began growing at an uncontrollable rate, forming a natural barrier. In some places, these "walls" of trees reached a thickness of fifty meters, cutting off the forest from the outside world. Meanwhile, a mysterious plague silently swept through the forest, infecting both animals and humans. Every infected creature began undergoing terrifying mutations.

The Soviet Union quickly established an investigative committee. Engineering corps were deployed to excavate a network of underground tunnels beneath the forest. By 1978, the tunnel system was complete. However, these tunnels were not designed for rescue operations; their sole purpose was to deploy investigation teams.

In 1987, the Maciek Squad received authorization from the investigative committee to enter the forest via the tunnels. However, the team was ambushed during their mission, and one researcher went missing. That individual, transferred from Warsaw, was never seen again, swallowed entirely by the forest.

Over time, the tunnels, for various reasons, were gradually abandoned. The forest's residents faded from public memory, leaving behind a desolate wasteland outside its borders. Overgrown with weeds, the barren land now only hosts abandoned guard posts, where crows perch silently. A rusted, weathered sign stands on the crumbling roadside, its faded text reading: "The Dark Forest."