Hydrogen sulfide (H2S) poisonings are classically reported in occupational settings. We describe an unusual domestic case of fatal acute poisoning by H2S inhalation. A mother and her infant daughter were found dead in the kitchen of their home. The emergency medical team described a strong smell of rotten eggs, suggesting acute H2S poisoning. Autopsies revealed only multiorgan congestion. H2S was measured in blood and lung tissue samples by gas chromatography/mass spectrometry. Body fluids were negative, but H2S was found in the lungs of both the mother and the child at concentrations of 1.46 and 1.92 mg/kg, respectively, concentrations described in the literature as potentially lethal. Expert surveys of the premises suggested a complex mechanism involving both defective maintenance of the pipes and drains of the building and faulty assembly of the sink siphon, which led to stagnation of waste water and formation of a pocket of H2S.