Forensic Files Season 2 Episode 5 Bitter Potion ( Air Date 1997-10-30 ) Genre Crime, Documentary category. Overview "The flu-like symptoms of a mother and her children proved to be indicative something much more serious: thallium poisoning. Investigators had to find the source of the poison... and when the mother died, to determine if the exposure was accidental, or if they also needed to find a killer.".