In Season #4 (1996-97), the D.O.A.s are mounting and America s favorite medical sleuth tracks down murderers, while simultaneously battling deadly epidemics ... and becomes an assassin s target himself. It s a prescription for intrigue.   Guest Stars: Ken Howard, Julie Benz, Lesley-Anne Down, Tracey Gold, Eric McCormack, Piper Laurie, Andy Griffith (as Ben Matlock), Mike Connors (as Mannix), Barbara Mandrell, Carey Van Dyke, Shane Van Dyke, Chad Everett, Jack Klugman, Tim Conway and Harvey Korman.