PARIS — Mary Fallot looks as unlike a terrorist suspect as one could possibly imagine: a petite and demure white Frenchwoman chatting with friends on a cell-phone, indistinguishable from any other young woman in the café where she sits sipping coffee.
And that is exactly why European antiterrorist authorities have their eyes on thousands like her across the continent.
Ms. Fallot is a recent convert to Islam. In the eyes of the police, that makes her potentially dangerous.
The death of Muriel Degauque, a Belgian convert who blew herself up in a suicide attack on US troops in Iraq last month, has drawn fresh attention to the rising number of Islamic converts in Europe, most of them women.
"The phenomenon is booming, and it worries us," the head of the French domestic intelligence agency, Pascal Mailhos, told the Paris-based newspaper Le Monde in a recent interview. "But we must absolutely avoid lumping everyone together."
The difficulty, security experts explain, is that while the police may be alert to possible threats from young men of Middle Eastern origin, they are more relaxed about white European women. Terrorists can use converts who "have added operational benefits in very tight security situations" where they might not attract attention, says Magnus Ranstorp, a terrorism expert at the Swedish National Defense College in Stockholm.
Ms. Fallot, who converted to Islam three years ago after asking herself spiritual questions to which she found no answers in her childhood Catholicism, says she finds the suspicion her new religion attracts "wounding." "For me," she adds, "Islam is a message of love, of tolerance and peace."
It is a message that appeals to more and more Europeans as curiosity about Islam has grown since 9/11, say both Muslim and non-Muslim researchers. Although there are no precise figures, observers who monitor Europe's Muslim population estimate that several thousand men and women convert each year.
Only a fraction of converts are attracted to radical strands of Islam, they point out, and even fewer are drawn into violence. A handful have been convicted of terrorist offenses, such as Richard Reid, the "shoe bomber" and American John Walker Lindh, who was captured in Afghanistan.
Admittedly patchy research suggests that more women than men convert, experts say, but that - contrary to popular perception - only a minority do so in order to marry Muslim men.
"That used to be the most common way, but recently more [women] are coming out of conviction," says Haifa Jawad, who teaches at Birmingham University in Britain. Though non-Muslim men must convert in order to marry a Muslim woman, she points out, the opposite is not true.
Fallot laughs when she is asked whether her love life had anything to do with her decision. "When I told my colleagues at work that I had converted, their first reaction was to ask whether I had a Muslim boyfriend," she recalls. "They couldn't believe I had done it of my own free will."
In fact, she explains, she liked the way "Islam demands a closeness to God. Islam is simpler, more rigorous, and it's easier because it is explicit. I was looking for a framework; man needs rules and behavior to follow. Christianity did not give me the same reference points."
Those reasons reflect many female converts' thinking, say experts who have studied the phenomenon. "A lot of women are reacting to the moral uncertainties of Western society," says Dr. Jawad. "They like the sense of belonging and caring and sharing that Islam offers."
Others are attracted by "a certain idea of womanhood and manhood that Islam offers," suggests Karin van Nieuwkerk, who has studied Dutch women converts. "There is more space for family and motherhood in Islam, and women are not sex objects."
At the same time, argues Sarah Joseph, an English convert who founded "Emel," a Muslim lifestyle magazine, "the idea that all women converts are looking for a nice cocooned lifestyle away from the excesses of Western feminism is not exactly accurate."
Some converts give their decision a political meaning, says Stefano Allievi, a professor at Padua University in Italy. "Islam offers a spiritualization of politics, the idea of a sacred order," he says. "But that is a very masculine way to understand the world" and rarely appeals to women, he adds.
After making their decision, some converts take things slowly, adopting Muslim customs bit by bit: Fallot, for example, does not yet feel ready to wear a head scarf, though she is wearing longer and looser clothes than she used to.
Others jump right in, eager for the exoticism of a new religion, and become much more pious than fellow mosque-goers who were born into Islam. Such converts, taking an absolutist approach, appear to be the ones most easily led into extremism.
The early stages of a convert's discovery of Islam "can be quite a sensitive time," says Batool al-Toma, who runs the "New Muslims" program at the Islamic Foundation in Leicester, England.
"You are not confident of your knowledge, you are a newcomer, and you could be prey to a lot of different people either acting individually or as members of an organization," Ms. Al-Toma explains. A few converts feel "such a huge desire to fit in and be accepted that they are ready to do just about anything," she says.
"New converts feel they have to prove themselves," adds Dr. Ranstorp. "Those who seek more extreme ways of proving themselves can become extraordinarily easy prey to manipulation."
At the same time, says al-Toma, converts seeking respite in Islam from a troubled past - such as Degauque, who had reportedly drifted in and out of drugs and jobs before converting to Islam - might be persuaded that such an "ultimate action" as a suicide bomb attack offered an opportunity for salvation and forgiveness.
"The saddest conclusion" al-Toma draws from Degauque's death in Iraq is that "a woman who set out on the road to inner peace became a victim of people who set out to use and abuse her."