HERCULE POIROT, mystery drama, based on the novels by Agatha Christie. BROADCAST HISTORY: Feb. 22-Oct. 14, 1945, Mutual. 30m, Thursdays at 8 until Oct. 7; then Sundays at 9. April 1, 1946-Nov. 21, 1947, CBS. 15m, weekdays, various evening timeslots. Mystery of the Week. Continuations told in five-chapter stories, concluded each Friday. Procter & Gamble. CAST: Harold Huber as Poirot, the supposedly ingenious but decidedly immodest Belgian detective. DIRECTOR: Carl Eastman.