Mysterious deaths are occurring in Basel: people are dying out of the blue in public with no apparent cause of death. The coroner, Professor Rüegg, the cantonal doctor Zäslin, and politicians are at a loss and becoming fearful. There are even serious considerations to cancel the upcoming carnival. Rüegg's assistant Andreas Zinstag, who is also dealing with the deaths, lives with his uncle, Jean-Jacques Zinstag, a retired doctor. The latter begins to take an interest in the mysterious deaths. Among his friends, Zinstag develops the theory that people are not dying from a specific disease, but from "death" itself. The Grim Reaper himself is making his presence felt in Basel, as he once did in the Dance of Death.