Some actors fear if they play Sherlock Holmes for a very long run the character will steal their soul, leave no corner for the original inhabitant -- and when the role ends, leave them unable to act without a pipe and a deerstalker cap.

"Some actors are 'becomers' -- they try to become their characters," said Jeremy Brett, who first played the Arthur Conan Doyle detective on television nine years ago. "When it works, the actor is like a sponge -- squeezing himself dry to remove his own personality and then absorbing the character's like a liquid."

Brett's success in becoming Sherlock Holmes can be measured tonight (Channel 26 at 9; Channel 32 at 9 tomorrow night) in "The Illustrious Client," the first of five episodes from "The Casebook of Sherlock Holmes." The new "Mystery!" series will air Thursdays through Dec. 12. Brett stopped in town recently on his 10-city U.S. tour to be toasted at the British Embassy, to smoke approximately 190 cigarettes and to offer clues to his role over a cup of coffee at the Park Hyatt.

When he did the first series, Brett did worry about being possessed by Sherlock Holmes. "Many actors -- Basil Rathbone for one -- think the role is bad luck -- the stigma of Macbeth," he said. Brett doesn't think he's ideally cast in the role. "To me Basil Rathbone is You Know Who. Yet, S.H. has been good for me." Lest ill fortune ensue, he doesn't refer to the detective directly, using instead circumlocutions such as "S.H." and "You Know Who" -- in the manner of Shakespearean actors who call "Macbeth" the Scottish Play.

Even so, Brett is hoping to be the first to play the famous detective in all the Conan Doyle oeuvre -- four novels and 56 short stories. This is his sixth series, bringing the collection so far to 34 works. He's filmed six episodes more that haven't been shown in the United States. Brett hopes to refilm the best of the novels, "The Hound of the Baskervilles": "We did it early on and I am not satisfied with it."

In "Mystery's" version of the Holmes stories, unlike some the performer won't name, the deerstalker hat is properly relegated to the country -- the bowler and the top hat are correct for town. A long frock coat was made of thin material so Brett wouldn't cook under the studio lights -- he wears it with a dickey and no shirt.

Except for his height -- he's 6-1 -- off-camera Brett doesn't really resemble the gaunt Holmes. To preserve a lean and hungry look, Brett doesn't eat lunch. During the filming of the series, he avoids temptation by eating an apple and taking a nap in Sherlock's bed.

Holmes is right-handed, Brett left. Holmes smokes a pipe, Brett doesn't. After trying long and hard to write a note with his right hand, he had a double do it. As for the pipe, his brother gave him lessons and mellow tobacco.

Brett has a generous shock of chestnut brown hair that falls over his forehead with abandon. For Holmes, he slicks it back. "At first I used rather a lot of makeup -- white on my face, a line down my nose to make it look aquiline, a pale violet shading. And four layers of white on my hand. I looked like a gargoyle." He's worked on the makeup, warming it up.

The character presented deeper problems. A fellow actor told Brett, "Holmes is hollow, an edifice. You have to invent a life for him." And he did.

As for why Holmes stays away from women, Brett postulates that he was once scorned. In one adventure coming to "Mystery!" next year, a woman kisses Holmes. "What do you think he does?" asked Brett. "He cries."

How Sherlock Holmes moves when the game's afoot took Brett a while to figure out.

He twisted his face into the Holmesian expression. "Let me see," he said, pulling up out of his prodigious actor's memory Conan Doyle's words: "He moves through the bracken like a Golden Retriever in search of a dead bird." Brett, however, decided on a panther. "Though first I made the mistake of taking too many short steps."

Today, Brett said, "encroaching age" has slowed him down. In one episode he was to run across the garden and "leap 20 feet over a wall. I said, 'I'm 55 -- I don't bounce any more.' They got me a double."

He also had a double for the famous struggle with Moriarty at the Reichenbach Falls -- "they locked me in the hotel so I wouldn't come to see it filmed. It was brilliant! How they could endure dangling on wires 300 feet long in that ice-cold glacier water!"

Brett has lived other lives in his career on the boards, playing a Who's Who of romantic characters: "Rebecca's" Max de Winter, Dracula, Dorian Gray, Hamlet, King Arthur, D'Artagnan, Freddie in the film version of "My Fair Lady," Prospero and Dr. Watson -- "I am always surprised when I realize I'm not wearing knee pants," he said.

His postgraduate course in acting included appearing with Laurence Olivier in the British Royal National Theatre. In his pocket he carries a note from Olivier to wish him luck in "Love's Labour's Lost." A fan had it laminated for him, but Brett isn't sure he liked that. "It was wonderful to be able to actually touch it."

Olivier addressed him in the note as "darling" -- "that's actorish, you know," Brett said -- and laid down the rules for acting. Most of them begin with "Do Think" -- except for one that says "Do Blaze."

When first asked, Brett was not terribly interested in taking on the Holmes television role. Then he spent a vacation in Barbados with an elderly friend who had a set, leather-bound, of the complete works. "I read every story. When I was asked again, I said yes."

When Brett began his first series, Holmes tried to take him over. "My wife told me I should go back to the hotel every night and have a celebration to get rid of S.H.," he said. "I would wash that man right out of my hair, escape his black-and-whiteness by putting on a red sweater -- and down a half bottle of champagne. After two more series it took me a whole bottle of champagne every night. And then I understood why Holmes took cocaine -- to rest his speeding brain so he could sleep."

Brett became worried about the influence of Holmes's cocaine habit on children. Everywhere he goes, he finds young Holmes fans and he gets hundreds of letters, which he tries to answer. He consulted with Dame Jean Conan Doyle, daughter of the author. She too was concerned. So in last year's "Devil's Foot" episode, Holmes renounced cocaine. "Perhaps some day, I'll quit smoking," he said. (Holmes might give up his pipe, but it seems unlikely that Brett would put out his cigarettes.)

The life of the strolling player makes it difficult for the real person to have a life of one's own.

While Brett was filming "The Final Problem," his second wife, Joan Wilson -- the executive producer of "Mystery!" and "Masterpiece Theatre" -- was found to have cancer. While she was being treated in Boston, he appeared in a U.S. production of the play "Aren't We All," with Rex Harrison and Claudette Colbert. "We thought she'd won, but she caught a chill and died on July 4, 1985. I was in shock -- seriously ill. After 10 weeks, I thought, if I could just get back to Manchester. ... 'Best, old boy, you get back on the bike.' I did five more episodes with ill grace. I resented You Know Who."

Since then, Brett's come to terms with S.H. He used to give interviews saying he wouldn't cross the street to meet Holmes. But now, Brett said, "He wouldn't cross the street to meet me."

But surely at this point, with Dame Jean Conan Doyle saying, "You are the Holmes of my youth," and 83 countries hanging on every clue, Brett is satisfied with his presentation of You Know Who?

He shook his head dolefully. "I am but a brass rubbing of Holmes."