ON THE RAW, gray morning after two ghastly accidents had all but wiped out the city, people were hanging on to one man, somebody they never heard about before Jan. 13.

He is Martin Skutnik, called "Lenny." He is 28 years old, a messenger at the Congressional Budget Office. His heroism at the 14th Street Bridge was one bright patch on a black day.

People who watched, over and over, scenes from the two refrigerated horrors -- death in the frozen Potomac, death in a dark tunnel -- stopped flinching and shivering only during the sequence in which Lenny Skutnik appeared.

A group of rescue workers are standing on the river bank. A few yards offshore, a woman is floundering amid the ice floes. The helicopter lets down a life preserver. The woman grabs it, but it slides out of her hands. The helicopter tries again. She does not have the strength, maybe not even the will, to grab it.

Suddenly, a young man is breaking away from the group. He plunges into the river. He swims strongly towards the woman, who has laid her head back on the water. He reaches her, seizes her, and heads for the shore. A man in a yellow slicker rushes forward to meet them with a rope. The woman, whose eyes are back in her head, is laid down on the snowy slope.

Salvation.

Skutnik was taken to the hospital, treated for exposure, and inevitably came before the cameras. He is a perfectly ordinary-looking young man in a sheepskin coat. He has a mustache, a husky build. His manner is modest to the point of humility.

On "Nightline," he is importuned by the perfectly coiffed host to say "what was going through your mind" before he dived into the frigid water.

Skutnik was having none of it. He had made his statement by his plunge. It was simply that he had seen the frustration of the rescue team. None of the ropes were long enough to reach the victim. As to "what you were thinking" when he got to the shore, he remarked matter-of-factly, "I was relieved I got her out."

The Congressional Budget Office people were pretty puffed up about Skutnik's feat. So were all the other government workers in Washington. One of them had shown what stuff there is in the despised bureaucracy, most of which was branded "nonessential" when Ronald Reagan showily closed down the government on Nov. 23.

The director of the CBO, Alice Rivlin, called up to congratulate him. So did his immediate boss, Stanley Gregg, head of the Intergovermental Relations Section, where Skutnik has worked since the spring of 1980. Previously, he did construction work, and for a while he had a clerical job in the Arlington office of the Social Security Administration.

Gregg reports that Skutnik is exemplary on the job, "gets in early, is always thoughtful and pleasant, never grumbles."

Rivlin and Gregg gave him an extra day of annual leave -- he was taking a few days anyway. They felt even the president would approve.

Skutnik told Gregg that he was inundated by calls and invitations to appear on television shows. He doesn't want to travel the celebrity route. His wife said he's the kind of man everybody in the neighborhood goes to when they have trouble.

He happened to be there to save a woman's life because he was on his way home to Lorton. Like the rest of the government, he had been let out early because of the blizzard. When he saw the fearful commotion at the bridge -- ambulances, helicopters, passengers bobbing in the water -- he stopped his car, got out and joined the frustrated workers on the bank.

He watched for a while, then shucked off his coat and his boots and dived in. Lucky for all of us, he was not one of those bystanders who hears cries for help and pass on. He got involved.

He plainly doesn't think there is anything special about what he did. His attitude, and we must hope it is contagious, seems to be, "Wouldn't anybody?"

On a killer day, in a brutal winter, he threw us all a lifeline by reminding us that decency is not dead. He may get the glory treatment whether he wants it or not. Television crews may stake out his house. Public officials will wish to be seen with him. We are painfully short of heroes, of examples of valor and mercy.

Little else about Jan. 13 bears thinking about. An ambulance official said somberly about the subway victims that they may have been trampled to death. A passenger, who survived the crash, and is himself a pilot, said from his hospital bed that he thinks the pilot of Flight 90 thought of aborting the takeoff seconds too late. The divers didn't have heated suits.

The day brought another hero, an unknown man who directed the helicopters to passengers he thought in greater need. He sank before he could be rescued. We know about Lenny Skutnik. We thank him for his presence on Doomsday.