Ann Fahey was a woman with a secret. The scheduling secretary for the Governor of Delaware was also having an affair with a well-known lawyer that came from a well known, wealthy family. Tom Capano, the killer decided to kill her after she ended their relationship.
She was last seen alive on Thursday, June 27, 1996, when she went to dinner with Capano in Philadelphia. Capano, the last known person to have seen her alive, was the primary suspect. Capano was arrested for her murder in November 1997, over sixteen months after her disappearance. However, Fahey's body was never found, and prosecutors were unable to establish the cause or manner of Fahey's death.
Prosecutors alleged that Capano murdered Fahey at the house he rented and, with the assistance of his brother, Gerry, dumped her body in a fishing cooler in the Atlantic Ocean.
This case was HUGE in and around Delaware, here's a great source of material to learn more about the case.