Quand sort la recluse

Three elderly people died a few months apart after a spider bite, the loxosceles rufescens. The small world of arachnophiles is in a panic: how could his attack have been fatal? Could the bug have mutated after ingesting too much pesticide? Adamsberg's hypothesis is obviously more prosaic. Could the spider have had a good back? He seems convinced that these three accidental deaths actually conceal a series of murders. It doesn't take much more for him to launch into an investigation, much to Danglard's chagrin, not really convinced by his point of view...