What people we have read about in this season of spies and terrorists -- a father who recruits his own children to spy for the Soviets, a lover who plots to blow up his unsuspecting "fiancee" and unborn child. Who is the greatest villain -- Nezar Hindawi or John Walker?

Hindawi is the good-looking 31-year-old Palestinian who pretended to be in Britain "to perfect his English." He wooed and won a pretty Irish chambermaid, Ann Murphy, at his London hotel. They became lovers, and when she became pregnant, Hindawi proposed that they marry -- in Israel. They would fly separately to Tel Aviv. He would meet her there. He booked her on El Al Airlines.

Moments before the plane's departure, Israeli security agents at London's Heathrow Airport, searching Ann Murphy's hand luggage for the third time, found a cleverly concealed bomb powerful enough to destroy Ann Murphy and all the other passengers on the El Al jumbo jet.

In fact, Hindawi already had a wife and child, a Polish woman and a 7-year-old son, with whom he lived in Spain. Terrorism apparently runs in Hindawi's family. A brother -- Ahmed Hazi -- was arrested for the Berlin disco bombing. The brothers had grown up in Lebanon, in camps run by the United Nations for Palestinian refugees. Both had Syrian connections and European wives, which seemed to bear out the warning in Jane's magazine that Palestinian terrorists were marrying European women to facilitate their movements.

I suppose it should shock no one that terrorists who kidnap and kill for political purposes should also betray the women who love them. Still there is something especially repellent about a man who coolly plots to destroy his unborn child and a woman who believes she is en route to marry him.

It is no more shocking than John Anthony Walker's efforts to recruit his own son and daughter to spy for the Soviets. Michael Lance Walker, who was only 13 when he first heard his father was a spy, joined the Navy at his father's insistence and then agreed to supply classified documents for $1,000 a week. "I did it for money and to please my father," the 23-year-old former seaman testified. "My father was pleased I actually had the guts to do it."

The elder Walker has said spying was a "simple matter." He just made copies of secret code materials and sold them to the Soviet Union. Recruiting his brother Arthur Walker and his friend Jerry Alfred Whitworth was easy enough, but efforts to involve his daughter failed. Walker kept trying, urging her at one point to undergo an abortion to remain in the service, threatening to kill her husband at another. He was "so persistent," she said, "there were times when I felt broken." The daugher resisted but never turned Walker in to the authorities, "because he's my dad."

"We should abandon all sentimentality in our views of the traitor," wrote the distinguished English journalist Rebecca West, "the traitor can change a community into a desert haunted by fear. . . ."

There are differences between the two cases. Walker did not try to kill his children, only to seduce them into treason. But terrorists and traitors -- like the Walkers, Whitworths, Peltons -- share some important characteristics. Both operate by deceit and bad faith. Their work depends on deception. Spies pretend to be loyal to gain access to secrets. Terrorists pretend to be airline passengers, truck drivers, unarmed civilians to gain access to their victims.

Because they operate in stealth -- pretending to be ordinary people living by ordinary rules -- spies and terrorists knowingly steal secrets and blow up planes, they betray our trust in one another and undermine our confidence that it is safe to go about our normal lives. That is the reason terrorism inspires fear disproportionate to the objective dangers it creates and why traitors cannot be tolerated.

It is also why loyalty and good faith are not just poersonal virtues, but are the very ground of public order.

Obviously, democratic societies must protect themselves against these threats to security and public order, and must do so in ways that do not restrict the freedoms they seek to preserve.

The first step is to be clear about the nature of the crime. "The man tempted to become a traitor will be helped if public opinion keeps it clear beforehand that treachery is a sordid and undignified form of crime," Rebecca West wrote. Presumably the Hindawis and Walkers of the world help us rid ourselves of any lingering sentimentality about such "political" crimes and criminals.