The courtship is always a whirlwind. He is handsome, charming, confident. His love letters are filled with longing. The flattery flows. You are smart. You are beautiful. You are his ideal love.

Master of the grand gesture, he whisks you off on romantic weekends. Mid-Atlantic, he pulls out a little present for you, just as the stewardess fills your glasses with wine.

You have no idea that he is a psychopath: deeply narcissistic, devoid of real feeling, a romantic predator. Why would you? He is your dream man.

He could be a she. The disorder has been studied more in men, but psychiatrists believe female psychopaths are just as prevalent, says Dr. Robert Hare, author of Without Conscience: The Disturbing World of the Psychopaths Among Us, and other books. A retired psychology professor in British Columbia, he is considered a world expert on the condition. He has studied the psychopath who lives next door, who sleeps in your bed, who works in the cubicle next to yours.

Society only points to the extreme cases of psychopathic behaviour, the violently criminal ones, the Paul Bernardos, the Charles Mansons, the fictional Hannibal Lecters.

But there is a garden variety. In her 2005 book, The Sociopath Next Door, Dr. Martha Stout writes that this "non-correctable disfigurement of character" is now "thought to be present in about 4 per cent of the population - that is to say, one in 25 people."

By comparison, the much-publicized disorder of anorexia, considered a significant societal problem, is estimated at 3.43 per cent.

The psychopath is unaware of his condition, of course.

He is not a criminal. He is charismatic, loquacious, intelligent. He thinks he is wonderful.

Your friends are charmed, too. What a sensitive soul, they say. How intuitive. How ambitious. He possesses all the characteristics most admired in people.

You are swept off your feet. "We are not the norm," he might say. You two are the special kind of people, he murmurs. He proposes marriage. Perhaps he drops to one knee on a beach in Bermuda, a diamond ring in his pocket, as if just a pebble. It's like a scene from a movie.

And yes, sure, maybe you hear a little warning voice in your head - that this guy is too much, that he is too smooth - but you ignore it, because, well, you are likely quite young. You are lacking in self-esteem, uncertain, just out of a relationship perhaps, or newly arrived in an unfamiliar city, or you are a single mother.

You are vulnerable in some way, and somewhere deep down you feel you do deserve this, you are special. He is in command, like a real man, you figure. He knows what he wants. He will make your life wonderful. Which is sexy. No one has ever loved you like this before. It's like a drug.

You carry the intoxication around like a secret. It sustains you. Truth be told, you feel a little sorry for other people who don't get to experience this level of passion.

After all, you think, this is how romance should be - overwhelming, undeniable, big.

It's only later, when in a marriage or in the daily routine of a relationship, that you notice things aren't quite right. He blames others for problems he encounters. He spends a lot of money, even when the family is struggling financially.

Perhaps he is in and out of jobs. If he runs into trouble at work, over questions about what he claims as expenses, for example, he blames the accountant. If his contract is not renewed for not doing a job he was employed to do, he suggests the guy who hired him was confused about what he said his skills were. The boss was stupid, he suggests.

He plays people and the system, and never takes responsibility for his actions. He lies. He is highly manipulative and prone to bursts of anger.

You also discover how critical he is of you. The torrent of verbal abuse is as fluid as the flattery once was.

You begin to believe that something is wrong with you. You think if I am just thinner, or if I dress better, he will love me again. Maybe you draw in your journal a picture of yourself with a big hole in your middle. You feel utterly alone.

You read mountains of self-help books, about anger, about love, fear, about making your marriage work. You feel confused. Why did he say that? Why did he do that? What have I done to make him so angry?

If you mention your distress to friends, and the fact that you're considering a divorce, they all say: "Oh, if you leave him, he'll be snapped up in a minute. He's such a great guy." To them, he is, of course. The shrinks call this "impression management."

What you must do is read Hervey Cleckley's book The Mask of Sanity, written in 1955 and still considered the seminal text on the syndrome. It will all start to make sense. You will be shocked. You consider yourself intelligent, and yet you missed this. Your partner was a textbook psychopath, and you didn't see it. You thought he was the love of your life.

Dr. Hare disagrees with Dr. Stout about 4 per cent of the population having this syndrome. Using PCL-R (or Psychopathy Check List, Revised), a precise measurement of the cluster of behaviours that together allow for a medical diagnosis of a psychopathic personality, he says the prevalence is more like 1 per cent of the general population.

"Whether one is a psychopath or not depends on how many of these characteristics one displays," he explains. But he admits: "A person may not have to have all of them to be a real problem in a relationship."

The psychopath is a parasite, looking to get something from you - sex, money, stability or status, Dr. Hare says. "People have weak spots, vulnerabilities, and buttons that can be pressed, and these psychopaths are looking for the buttons to press."

Here's the good part, though. It may be difficult to ditch him (he will turn on the charm again when he senses you might leave; he will do what he can to manipulate you into staying), but when you stand up to this emotional bully and get free, you can be assured of one thing. He will quickly move on. He will replace you. He won't think about you and he will become someone else's problem.