Lucens, Switzerland, 21 January 1969. On this day, there was an accident at a nuclear research reactor comparable to the meltdown in Chernobyl or Fukushima. As the reactor was in a deep tunnel, it could be closed off before radioactive radiation leaked out. The incident was kept secret and to this day is unknown to the public. The film, set in the year 2023, is based on these events.

The psychologist Marta is assigned to visit a tunnel construction site that is emitting an unknown mixture of air and gas and has caused climate changes in the area. The entire valley has been evacuated. Marta is to look for the three remaining engineers who are displaying symptoms of disorientation and paranoia.

Marta herself had also participated in a biosphere project. During the isolation, the functions of her psychic memory were so badly damaged by the reduced oxygen levels that she suffers from hallucinations and can no longer determine between memories and desires. Her penetration into the tunnel system also becomes an obsessive search for the traces of personal loss. The more she loses her orientation in the tunnel, the more her memories and projections of desire overlap.

The fiction of the film, which is inspired by science fiction films from the 1960s, revolves around the possible effects of the loss of natural environments on individual and collective perceptions.