Murder, She Wrote (1984)

Season 11: Episode 1

When Jessica spends some time at a zoo researching her latest novel, she soon gets drawn into a case of murder when the body of Mark Atwater, the fiancé of one of the zoo workers, is found murdered (death by snake venom), and another employee is charged with his murder. In the course of her investigation, she soon learns that a number of people had a motive to want Mark dead.