The time was 1 a.m. last Nov. 10 A District of Columbia woman was asleep in the second floor bedroom of her comfortable Shepherd Park home when she was suddenly awakened by a man who held a knife to her throat.

"If you want your children to live, don't say a word," the intruder told the woman, whom he then raped once in her bedroom, once again in her basement, and a third time on the first floor other home, according to a police account of the incident.

Two weeks ago, another Shepherd Park resident heard a noise in an upstairs room about 9:45 a.m. She walked upstairs to investigate and was raped by a man who threatened to kill her if she failed to stand silently in a closet while he escaped.

And this Wednesday, in the neighboring Takoma area of the city, an elderly woman was raped by two men who roused her at 6 a.m. accordingto police records.

These three assaults are part of a string of 12 rapes that have occurred over the last year in three upper Northwest neighborhoods - Shepherd Park, Takoma, D.C., and Brightwood.

Police believe several men are responsible, but detectives working to solve the crimes refer to their suspects as the "Wake-Up Rapist" because many of the victims have been startled in the middle of the night or early morning.

Two of the most recent assaults, which occurred on June 28 and July 13 within a two-block area of Shepherd Park, have sparked organizing efforts among citizens who live in the affluent area. They are determined to fight the crime spate of violent crimes that have spread alarm, and in some cases panic, through their neighborhood.

Two weeks, one meeting, two handouts and a gaggle of phone calls later. Shepherd Park residents are recasting old habits, locking their doors, windows and cars religiously exchanging information with police, and lauding the cohesiveness they say has sprung from their preventive efforts.

"People started to think again what a community, a neighborhood really means - talking, sharing, being concerned about the next person, "said Harriet V. Washington, executive assistant at Neighbors, Inc. a community group in upper Northwest.

Along with the renewed togetherness in Shepherd Park, however, has come a sharpened sense of the neighborhood's vulnerability to the crimes that occur more frequently in other parts of Washington.

Shepherd Park is an upper-middle-income, integrated neighborhood that extends north from the intersection of Alaska Avenue and 16th NW to the District line. Its recent community-based efforts to combat crime are not unlike what other neighborhoods in Washington, such as Adams-Morgan, have tried to do enhance their security.

Last Monday, D.C. police arrested 18-year-old Joseph Jordan of 6907 8th St. NW and charged him with burglary and the June 28 Shepherd Park rape.

But residents of the community remain concerned and vow to maintain their vigilance. "We won't take for granted that this (arrest) is going to erase this kind of situation from our neighborhood." said Katie Fisken, one neighborhood resident. "We still have to keep in close touch with one another."

Police Detective David S. Brown, one of the officers investigating the Shepherd Park rapes, said that as long as most of the assaults remain unsolved the areas residents should remain cautious.

Efforts to bolster neighborhood security date back to last fall, after a rape in Takoma, D.C. and three other rapes in the Shepherd Park Elementary School area, which embraces Shepherd Park, Colonial Village and North Portal Estates. In two of the rape cases, the victim was awakened by her assailant.

The last of these victims, a resident of Shepherd Park recalled that she was "thunderstruck" when police told her of the other rapes in the area. "I just found it hard to believe these things happened so close to me and I had not known about them," she said. There was, she added, a "communication problem."

The rape led to an article in the Neighbors, Inc., newsletter and warnings to residents of a three to four block area to take security measures. But many residents of Shepherd Park assumed the assault was an "isolated incident" and so relaxed their vigilance, said Susan Learmonth, a resident of the neighborhood.

The latest series of rapes began in early May. Over the next month and half, three women in Takoma and one in Brightwood, a neighborhood south of Shepherd Park, were assaulted.

But the community reaction came only with the rape of two Shepherd Park neighbors. "Suddenly you get two (rapes) together in a matter of a week or a week and a half," said Harriet Washington. "It was the second one people reacted to. People really became concerned.

"The night of the July 13 assault, Fisken and a friend, Janet Crockett, decided that it was ridiculous not to contact police and spread word of the rapes and a description of the assailant, Fisken said.

Using skills she picked up as a Peace Corps worker in India in the mid-1960s - "that was the best investment the U.S. government ever made," Fisken said - the 35-year-old part time teacher and Crockett contacted one person per block and asked each to call two friends.

"There was an overlapping of effort, which was terrific." said Fisken. "We wanted to bring home the idea that this was something serious and we wanted to get the neighborhood actively organized." Others also responded to the news. The victim of the rape last fall called Neighbors, Inc., "after a week of trying to force myself to do it," she said. She was anxious that the word of the recent rapes be spread.

"If I hadn't done something, I couldn't have lived with the fact that it happened again." she said.

Several days later, a composite drawing of the suspect, photocopied by a handful of women and their husbands on Xerox machines in their offices and homes, was distributed to at least one person in each block. Each was then expected to show the drawing to her neighbors.

A leaflet was handed out at the Shepherd School polls on July 19, the day of the special City Council election. It carried the description and announced an open meeting with police the next day.

Despite the 90 degree heat that night, more than 110 people, two-thirds of them women, gathered in an unair-conditioned room in the Ethical Society building. "It was hotter in the building than outside," said Fisken. "It was important enough for people to want to participate."

The turnout was attributable not simply to the generally high neighborhood interest in local affairs but because "rape is something that is much harder to take than someone breaking into a house and taking objects," said Evelyn Wrin, advisory neighborhood commissioner for the area.

"Rape is an outrage," said another resident of the area. "There aren't many things in this age that you can become enraged about because the world is so impersonal. A rape is a very personal thing."

Since the 90-minute meeting, the rapes have become a frequent topic in conversations among parents in carpools and neighbors encountering one another outside their houses or in neighborhood stores.

And, at the same time, residents have begun locking up more carefully, worrying about having too many families on vacation at the same time in the same block, tending after empty houses so lights are on inside and newspapers do not pile up outside.

The victim of the rape last fall believes women in the area - and in the city generally - still "do not take it as seriously as we ought to." The women, who could not enter her own house for five days after being raped and even debated selling it, says, "It distresses me to see individuals who continue to do careless things."

In her case, the woman said, the rapist had stolen a key during an earlier burglary and could return again because she had not noticed that her key had been stolen and had not changed her lock.

She had not, she said, "paid close attention" to the fragility of her personal security. And sotoday she no longer feels completely at home in her own house.