Strange fatal cases of spider bites with elderly victims are observed in a provincial town in southern France. The fiery inspector Antamberg, urgently called from Iceland to take over the case of a woman's murder in Paris, turns his attention more to these unusual incidents. Once again, his intuition does not deceive him: something else is hidden behind these deaths, given that the poison of this particular spider - the so-called "hermit" - which is believed to have caused them, is not fatal.

With few allies from his team by his side, the inspector embarks on an irregular investigation which, in the course of it, brings to light new evidence, weaving a terrifying web around the case. The victims of the spider, elderly men who were all once prey in the same orphanage in the area, multiply and Antamberg, in his attempt to unravel the mystery, will be immersed in "a case that reaches the depths of the past and the mind"...