I also wonder what made the husband suspect nightshade poisoning specifically?
Nightshades contain solanines, which in high doses cause gastrointestinal symptoms as well as slow pulse, headaches, and fever. Now, if I experienced those symptoms, my first thought wouldn’t be nightshades. But if for some reason I suspected that I’d been poisoned, my first thought (until now) would be prescription medication or elicit drugs - not a poisonous plant. Therefore, SP’s mind jumping straight to nightshade poisoning suggests to me that perhaps EP has a known interest in or knowledge of plant poisons…?