Prisoner Alvin Dyson was puzzled. Sure, the letter was addressed to him at Lorton Reformatory, but the 42-year-old inmate didn't recognize the name of the woman who'd sent it. Curious, he turned the envelope over then tore it open as he shuffled forward with the other prisoners in the lunchtime chow line.

"You promised me you wouldn't get in any more trouble," the letter began. All of it was written that way, as if the woman knew him intimately. The weird thing was that some things she wrote about really did seem familiar. Maybe it was a joke or some crazy woman. Suddenly it hit him like a blow to the gut.

Dyson gave his plate to another inmate. Then, weak-kneed, he stumbled back to his dorm and found his way to a bathroom stall. Alone at last, he sat down on the battered toilet seat and began to cry, the sobs coming in great heaves that he tried to stifle so the other prisoners wouldn't hear.

The letter was no joke. It had simply been given to the wrong Alvin Dyson at Lorton.

Now he knew that his 20-year-old son Alvin Jr. was in prison with him.

"A man is not too big to cry, especially about someone this precious to him," said Dyson Sr., a tall man with a forehead scarred from two bullet wounds. "My life don't mean a damn compared to his."

In one of those tragic twists of life, Dyson sees his own failures as a father coming back to haunt him in the most painful way imaginable: by his son repeating his own mistakes.

Dyson is not alone. Lorton officials say they may have as many as 20 other inmates who can count sons among the 2,550 Lorton prisoners. Maryland and Virginia prison administrators say they, too, have father-and-son prisoner combinations, though they have no idea how many.

Statistics show that such coincidences, while rare, are to be expected from time to time. One study, for instance, shows that as many as one out of every 15 prisoners nationally is the son of a father who at one time has been incarcerated.

Those who conclude that prison fathers breed prison sons are mistaken, according to Stanton E. Samenow, a psychiatrist who has studied criminals for 10 years.

"We have kids from responsible families who end up irresponsible," he said.

Such assurances offer little comfort to the prison fathers who blame themselves for their sons' failures, said Lorton central facility administrator Salanda V. Whitfield.

"I think it's one of those types of difficult things for the father to accept," he said. "There's grief and guilt. He wonders, 'How much did my own incarceration play in that? Did the son see glamor in that?'"

Like most fathers, "the guys are very proud of their children," Whitfield continued. "They tend to blame themselves for the failures."

Not all prison fathers feel that way, he said. There are some who never have anything to do with their sons. For some sons being locked up at Lorton has actually provided them with their very first opportunity to meet their fathers, Whitfield said.

And sometimes the experience has brought father and son closer together than they ever were outside.

Whitfield said he remembers one father, a model prisoner, whose inmate son was a homosexual.

"The father had difficulty accepting it," he said. "He played the same role as some fathers in the community outside Lorton and tried to avoid him. He basically said, 'You are my son, but I don't want to be bothered with you . . . . ' "

Whitfield said that, when the man's son began "getting into some trouble, I asked him if he would talk to him . . . . Soon, a lot of the little problems that we had with the son stopped.

"In many cases, we find the fathers to be a positive influence. Even behind bars, they still play a limited father role."

Prisoner Marcus Nelson Sr., 45, has two sons in Lorton. The older is serving time in the central Lorton facility alongside his father, while the younger is being held in the Lorton youth center about two miles away. Nelson said he would rather that his younger son were with him, too, because "I could keep him out of trouble. Kids have a tendency to fall in with the bad group of guys."

Joseph Watson, another inmate, said he and his two sons slept in bunks side-by-side in the same central facility dorm until one son was released last week. It was important to keep his sons nearby so that he could look after them, he said.

Alvin Dyson Sr. feels the pain of his son's presence acutely, even though he cannot see his son because Alvin Jr. is in the nearby Youth Center. He said he has always been proud of his nine children but that his oldest son, Alvin Jr., has always held a special place in his heart.

"He's little Me Junior," said Dyson, who is serving up to 16 years in prison on convictions for armed robbery, grand larceny and unlawful possession of drugs. "I used to keep him walking with me all the time. I think maybe I did this because I never was with my father. I used to pick him up and put him in the car with me. He'd say, 'Let's go Dad, let's go.' And we would go riding. I would keep him around me all the time."

Dyson, whose son was raised in Northeast Washington, said his own father, now dead, also served time in Lorton. The first time he ever met him, he said, was when he was 3 years old and his mother took him to see his father in D.C. Jail.

"My mother was the dominant factor in my life," he said. "I was brought up in a strict home . . . . You couldn't play cards. You couldn't use profanity. I went to church three or four times on Sunday. I used to sing in choirs."

When he was out of prison he tried to see that none of his own children "got into trouble. Even though I was separated from their mother, I kept on top of them. I never refused them anything."

Even when he was imprisoned, he kept in touch. "I wouldn't allow them to visit me. I didn't want them to see these types of conditions. I called them and talked to them. Any money they needed I would send it to them. This is not a place for kids to see."

His prison tenure over the years caused repeated problems for his children, he said.

"The kids used to mess with my kids," he said. "They would say, 'Your father's a jailbird.' My kids got into a lot of fights behind that. But half of them those children who were taunting his own never seen their own father. The only person they ever knew was their mother."

"I didn't want him roaming the streets like other kids," he said.

Alvin Jr. eventually enrolled at UDC. Had he not been arrested and convicted, he would have been a junior this year, he said.

How did it happen?

"Hanging with the wrong crowd," said the muscular 6-foot-4-inch Alvin Jr.

Alvin Jr. was ordered to Lorton to await sentencing after being convicted of attempting to cash a stolen check.

Three months earlier, he had received a one-year suspended sentence for aiding in the theft of a brief case from a parked car.

"I told my dad," Alvin Jr. said. "He said, 'Boy, I told you about that. This is no place for you. This is no place for me. Please stay out of trouble because you broke my heart.' I didn't want him to find out about this. I knew it would hurt him."

"I don't think he wanted me to know," said his father. "But God moves in mysterious ways -- I got his letter . . . . He knows how I feel about jail and prison. He knows he has disappointed me because he had written me a letter and promised that he wouldn't get into trouble again."

Dyson Sr. got his first opportunity 11 days ago to talk by telephone with his son when a Lorton official arranged for him to get his son's approval before talking with a reporter about their lives.

"He was surprised," the senior Dyson said. "He said, 'Dad, I didn't mean nothing. I swear I didn't.' I said, 'Okay, son.' "

Like Dyson, Marcus Nelson never intended for any of his sons to end up at Lorton. But two of them did and he sees himself as responsible.

"I wasn't there," said the slim, bearded man whom inmates call Spot (they call his older son, Nathaniel Rogers, Little Spot). "Being incarcerated has caused me to neglect my family. I feel that if I had been there some of the things that happened to my boys would never have happened."

"When I was 9 and 10 years old, I would come to visit him," said Nathaniel, 25, who with his brother was raised in Southeast Washington. "I wanted my father home so bad. When it came time to leave to go back home, I used to cry and didn't want to leave him. And then I find myself in the same place he is. It's just a hell of a coincidence. I really love my father. But I didn't want to follow in his footsteps.

"I used to feel sorry for my father," the son said. "My father was one of the type of guys who was really a good guy and he wanted everything for his family."

His father always found an easy way to make money -- and that usually meant crime, he said.

"And that's where I made my mistake," Nathaniel said. "I wanted everything for my family . . . and I went out and tried to take it."

Nathaniel has been ordered to serve from 11 to 34 years for assault with intent to kill, armed robbery and carrying a firearm. His father is serving 18 months for petit larceny.

Marcus Jr., 20, is serving six years for petit larency under the Youth Corrections Act and is awaiting trial on an armed robbery charge.

Marcus Jr. said he has another brother who "has never been in no trouble . . . . Trouble just wasn't for him. Most of the time like when we didn't have no money or we needed something, he would go out and do little odd jobs. At that time, I didn't have no patience. I figured we needed it now and I couldn't wait."

So, Marcus Jr. said, he became a robber. He said he was arrested on about 40 charges as a juvenile. "I was young and crazy. Every time you turned around I was getting into something."

"Most of my life my father and brother have been locked up," he said. "My brother's been locked up about six years. My father's been locked up off and on. There's never really been a man in my life to tell me what to do."