The actress began her career in 1946 and semiretired in 1984 after more than 50 films, including "The Manchurian Candidate," "Touch of Evil" and "My Sister Eileen," and 30 television movies. She has spent the last decade writing. Her biography, "There Really Was a Hollywood," was published a decade ago, and a novel, "House of Destiny," partly about the movie business, will be released in the fall by Harlequin Press.

But "Psycho," with Hitchcock's bag of nerve-jangling cinematic tricks and the screeching score by Bernard Herrmann, is what she is remembered for. In the film, she played Marion Crane, a troubled woman seeking to break off an affair with Sam Loomis (John Gavin). One day her employer asks her to deposit $40,000 in the bank on her way home. Viewing the money as her ticket to freedom, she embarks on a trip to see Sam. A torrential storm causes her to miss the main highway, and she stops at a lonely motel run by Norman Bates (Perkins), who befriends her. Norman tells her he lives with his powerful, unbalanced mother. Realizing that she is as trapped as he is, Marion resolves to return home the next morning and face the consequences.

But that's tomorrow. Tonight, she'll take a shower. . . .

"Psycho" consumed Ms. Leigh for years. A casual meeting with some publishing friends in New York last year, when Ms. Leigh mentioned the mail she still receives about the film from viewers who have seen it on cable or home video, led her to do the book.

Seated in her Beverly Hills home, the actress said that while there have been numerous books about Hitchcock, including explorations of "Psycho," none have been written by an insider who was actually present at the creation of the film.

"I've been in a great many films, but I suppose if an actor can be remembered for one role then they're very fortunate," she said. "And in that sense I'm fortunate."