Of all the household, he alone would be likely to recognize the symptoms of strychnine poisoning, and yet we find him the only member of the family to uphold strenuously the theory of death from natural causes. 
In that situation, he would have no idea about strychnine poisoning.
mnli hypothesis: In that situation, he would have no idea about strychnine poisoning. premise: Of all the household, he alone would be likely to recognize the symptoms of strychnine poisoning, and yet we find him the only member of the family to uphold strenuously the theory of death from natural causes. 