A rash of unexplained deaths at a Northport, New York hospital in the 1990s and the suspicious death of a wealthy businessman in the 1840s have one thing in common: poison. These sensational cases, 150 years apart, are landmark moments in the history of forensic toxicology. Revolutionizing crime fighting, then and now, toxicology may one day be ahead of the crime. Join our investigation as scientists, detectives and criminal historians trace the poisonous compounds and indispensable tools of crime fighting.

• Denny Heide