DNA

A murder scene looks like the one that drove Joe Donovan into a breakdown -- except for the name "Donovan" scrawled on a wall in blood.

Another murder occurs in an identical fashion to the Gibson killing and suspicion falls on the Donovan family.

Donovan pursues a serial killer who only takes blonde women as his victims.

Stephen Parker is found shot and it seems like a robbery gone wrong, but Donovan suspects the victim's son.

A plane's passengers and crew are stricken by an unknown illness in a possible case of biological terrorism.