On the stairs to lunch, actor Sam Neill passes a pretty woman. She looks at him, stops cold, almost speaks, loses her courage, shakes her head and, smiling ruefully, goes on.

Does it happen all the time to Neill? Is he better known as Reilly, Ace of Spies, or Harry Beecham, the handsome landowner in the Australian film "My Brilliant Career"? Next month he plays Meryl Streep's long-lost lover in "Plenty." And this season, he stars in the CBS mini-series "Kane and Abel," set in Boston.

"It's not really that people recognize me so often but that I look familiar," says Neill, surely the most modest and unassuming of actors. "They can't quite remember where they knew me."

Neill looks very familiar indeed, though the tonsorial change from Reilly's '20s parted-in-the-middle, slicked-down haircut, to Neill's '80s rather boyish flop-over-the-forehead makes him look younger than his 37 years. At lunch his coat is broad-shouldered, his striped shirt tieless. The following day, at the embassy of his native New Zealand, he wears a cream-colored linen suit, with shoes to match: the Commonwealth costume for tropical Washington.

The Life of Reilly has brought him to Washington for a mini-series of appearances, including a fund-raising appeal tonight on WETA (Channel 26) following the concluding Reilly rerun. This is his first visit to the States outside of a brief filming in New York.

"The last time one of my family was in Washington, he burned down the White House and the Capitol," Neill said. The anniversary of the dastardly deed of his ancestor, Capt. Fyans, is, by coincidence, Aug. 24, 1814, the day Neill is leaving town.

Playing Reilly has led people, especially letter-writing women fans and casting directors, to have certain unrealistic expectations of him, he admits. "I do get a number of scripts with parts for a man with cold blue eyes that can drill holes through steel at 100 paces . . . able to make women collapse on the floor when he comes in the room.

"Actually Reilly in old photographs seem to have bulging, almost hyperthyroid eyes," Neill says.

The women diners in Aux Beaux Champs try hard to keep from staring. Neill pretends they aren't there. He's a master at the ultimate flattery, concentrating on the person he's with.

Neill doesn't seem so much unapproachable as unapproaching. When he speaks of his private life, for example, he refers to it sideways, explaining his knowledge of Virginia as coming from his "girlfriend," Lisa Harrow, who played Nancy Astor in last year's PBS mini-series filmed partly in Virginia. Neill and Harrow have a 2-year-old son.

"I'm a reasonable man," he says, "open to suggestion. The subject of marriage never has come up. We don't discuss it." Their son, he says, "has his mother's name. And mine. He has two surnames. That's better than me."

Unlike some people in the star business, Neill doesn't want to talk about his career, his eyes, his loves or what you think about him. He doesn't even watch his own films a second time. "Once is enough." He wants to talk about women's rights (he's for them and thinks good roles for actresses are too scarce), architecture (he wants to see Washington's contemporary buildings) and politics (he thinks "this is the most dangerous of times"). He manages to turn all questions about himself into reflections on issues of the day.

A New Zealand newspaper, Neill says, spoke of him as " 'daunting to meet, difficult to know.' " I was enormously flattered. New Zealand is a land of strong, silent men. We don't produce many actors, and certainly no exhibitionist types."

What would you expect? Both his father and his mother are ex-military. His father was a Harrow and Sandhurst graduate, a major in a British Army Irish regiment; his mother, a World War II captain. Neill's family was the traditional British Commonwealth type -- early New Zealand settlers (1850) who always sent the sons back to Harrow. "My father is quite an anachronism," Neill said. "He would have sent me to Harrow, but my mother wouldn't let him."

Instead, Neill went to a boarding school in New Zealand, where he began to act in school plays. "Acting was a way of expressing yourself. Boarding school doesn't altogether encourage you to open creativity."

During one summer, between attending the universities of Canterbury and Victoria, he worked in a town planning office. He "corded" hay for three others. He rode horses a great deal on his family's 20 acres. And he went to movies -- Alan Ladd and Dirk Bogarde by choice. Now he likes Jack Nicholson, he says.

"Acting has no precedence in my family. Mysterious business. I didn't train as an actor. It wasn't possible because there were no acting schools in New Zealand and I didn't have the money to go elsewhere. I suppose my parents had rather I be a lawyer, as a more reliable profession, but they seem to enjoy my acting."

At the New Zealand embassy he's counted a great national pleasure and a pioneer in the thriving film industry.

He speaks knowledgeably with Ambassador Wallace Rowling about the embassy's architect, Miles Warren, and the Maori sculptor Ralph Hotere. With Lady Glen Rowling, he looks carefully at the New Zealand paintings. Neill has what he describes as a "small collection" by New Zealand contemporary artists.

John Wood, a New Zealand diplomat, talks of Ngaio Marsh, known in the United States as one of the two or three best Anglo mystery writers, but in New Zealand known better as a great producer and director of Shakespeare. Neill knew Dame Marsh well, he says, and became serious about acting after working with her in "A Midsummer Night's Dream."

"She wanted us to declaim in 'a lilting voice,' " he says, doing so. "She deplored the New Zealand rather nasal speech. She herself spoke in a great basso profundo and smoked a pipe. I was in only one play with her, but she was so meticulous, we were in rehearsal for three months. She told you every place to stand and every movement to make."

You gather he makes every effort to speak well, because somewhere the late Marsh is listening.

Neill claims he has a typical New Zealand accent. He doesn't -- except when he's with other New Zealanders. "I think accents have a great deal to do with the climate," he says. "In the north of Australia and here he puts on a heavy dialect , "They have flies. So people don't open their mouths. The sun's bright so they squint their eyes. Now in New Zealand, it's damp and people have colds all the time. So they speak with a nasal accent."

As a Bostonian in "Kane and Abel," "I demanded a voice coach. I had no fear of doing a standard American accent, but to do one from a specific place and class, I wanted to do it just right."

Neill counts acting as hard work and appears not the least bit romantic about his occupation.

As a young man he acted for three years in New Zealand theater, playing Macbeth, among others. Then he worked for five years as producer, director and writer of eight or nine films, including a documentary on New Zealand architecture ("A mistake: buildings don't move") and as editor of many others with the New Zealand National Film Unit.

He is still interested in directing, producing and the other aspects of films, but "not theater. Lisa is interested in theater but I think it's boring." He says that "on a film set it's mostly sitting around and being bored," but it's "nice to watch other people do their jobs and learn from it." He's even written a screenplay, adapting Elizabeth Bowen's "The Last September."

As an actor, he reads a good bit on the subject of a role -- "I know the character and the background, all there is to know, his past and future." But he's not one to be possessed by the part.

"I don't take it outside the studio. My emotional involvement is not with the role, but the people I work with and the project. You have a responsibility as the leading actor. It's like being captain of a cricket team.

"I never have any trouble remembering who I am off camera, but I have made movies in so many places, I sometimes wake up in the middle of the night and wonder where I am."

He began acting in films in New Zealand in 1974. In 1977, he appeared in "Sleeping Dogs," the first New Zealand feature film in many years. He attracted international notice in 1980 with "My Brilliant Career."

James Mason saw the film and sent Neill a plane ticket to England, suggesting he try out for Damien Thorn in "Omen: The Final Conflict." Some critics think Neill looks and talks like a younger Mason. Neill's speech, softer than the traditional English theater accent, is full of hesitations.

Mason was right; Neill got the role. Neill says "The Final Conflict" was not very good, "but it took me to Europe." He values having known Mason before he died -- "a kind and generous man" -- and still is friendly with Clarissa Kaye Mason, a New Zealander who lives in Switzerland.

As for Meryl Streep, "I was slightly daunted by her at first. I think she's such a wonderful actress. On the set of 'Plenty,' though, I found she is funny and relaxed. We laughed all day long. I shouldn't have been surprised. One's image has really very little to do with anything at all."

At the moment, Neill isn't sure what's next. He, Harrow and their son Tim are just back from five weeks on the island of Harris in the Hebrides. He has a suitcase full of scripts to read. He'd like to drive across the United States like Jack Kerouac, but doesn't have time: he's on his way to check on the house he's building on 10 acres of land in New Zealand. His architect is a friend, Ian Athfield. "He's the most creative designer. But there's a problem. I favor rather more austere, classical design. He's more romantic. Since I'm paying for it, I think I should have my way. Like acting. The best director doesn't say where you should walk or how you should speak but helps you with the overall concept."

Before he says goodbye, he returns with determination to what he's wanted to talk about all along: world affairs.

He doesn't think of himself as a Jane Fonda or a Ronald Reagan. On the other hand -- "I think that as an actor, we live unworldly lives. And I come from a little country that is isolated. At the risk of sounding self-important or pompous, I say it helps one see the world, not in a simplistic way, but simply.

"I worry about the extinction of the species. I see insanity all around. Why can't Reagan and Gorbachev sit down together? New Zealand was one of the few allies who, rightly or wrongly, sent troops to Vietnam because the United States asked us to. But now, because the New Zealand government has made our country a nuclear-free zone, Washington is distressed."

It's not Reilly, Ace of Spies, but Sam Neill who says, "You can't separate politics from life. You have the responsibility to be involved. Especially if you have a 2-year-old son."