Ron and Michael Mastin began their marathon long before reaching the Hopkinton, Mass., starting line Monday morning.

For 42 years they've been on a hard course, where each hill and every curve came with the risk of one running off and leaving the other behind.

Ron, 67, is the father, the stoic Midwesterner with the fighter pilot's low heartbeat who for the last 27 years has lived in the Atlanta area. One thing that sets a quiet man apart from his Woodstock neighbors is the "Former POW" license plate on the car out front.

Michael is his 42-year-old son, still living in Kansas City. He's the sensitive soul who e-mailed the newspaper with a story that went far deeper than his old man's goal of running marathons at least until he's 70.

The synopsis of his message: A father and a son who had been separated first by war, then by the personal fallout afterward, were going to meet in Boston and take a 26.2-mile run together.

There were more than 25,000 entrants in Monday's Boston Marathon. This race, however, was going to be about two in particular, running in tandem through the New England countryside all the way to the John Hancock building.

Michael would need to slow his usual pace by as much as two minutes a mile to stay back with his father. But so what? There already had been too much time apart.

Stride for stride, shoulder to shoulder, the two crossed the finish line Monday, some four hours and nine minutes after they had started.

"A dismal time [for him], but a personal record for fun," the younger Mastin said by phone afterward.

Other marathons —- this was Ron's sixth and Michael's seventh —- were about running for time. This one, though, was about making up for time already lost.

"Dad in a way has always been a mystery to me," Michael said last week, before leaving to meet his father in Boston. "We didn't have that much time together to build our relationship. It seems like when we are together, it's like I'm always interviewing him, filling in things about the past. It's not like that when we're running."

For much of Michael's childhood, Ron was a mysterious figure, known to him only through old photos and family stories. He was just a little over a year old on Jan. 16, 1967, when Ron was shot down over North Vietnam. He was a prisoner of war until March 1973.

Michael's first sustainable memory of his father was the reunion at a Kansas military hospital, this almost mythical figure come to life, all 135 pounds of him.

Ron had been locked away in a series of camps throughout North Vietnam, isolated from the spasms of change in the U.S. He had missed six of his son's seven birthdays. His wife was a different person. "As my mom describes it, it was like he was frozen in a time capsule," Michael said. "My mom is an extremely dynamic woman. By the time he got back, she had turned against the war and was into the women's liberation movement."

Why, the first time Ron spanked his misbehaving son, it was like he was the one committing a war crime.

"He had never had a hand laid on him before. It was a strain at different times," Ron said.

Within a year of his return stateside, Ron was separated from his wife, soon to be divorced. Both would remarry. Ron briefly would return to active duty and then fly for Eastern and FedEx (now retired). His connection with his son, meanwhile, grew weaker as he settled in Georgia and began raising two daughters with his second wife.

They are very different people, products of their generations. Ron is a rock-ribbed conservative, his son a liberal stay-at-home father of two daughters who works construction part-time.

Still, with just a little effort, they discovered there was a lot to love about one another.

"I've got a lot of pride in everything he's done," Ron said of his son. "I really enjoy being with him. Even though he is a liberal tree-hugger, we have a good time together."

What they have in common is University of Kansas sports, and, it turned out, running. "He's better than I ever was," father says of son.

As was his way, Michael seized that common ground. It usually was up to him to reach out.

"I wasn't around when he was growing up, and I always felt he might take it the wrong way if I was pushing too hard," Ron said.

So the son suggested the two of them enter a few selected races —- but then continue on at their own pace. Once in California, once in Florida, once in Atlanta.

But it was Boston, the most famous marathon, for which Michael aimed. It was his dream to complete that classic race with his father, to run with him all the way. When Ron qualified last year and Michael failed —- the qualifying time for his younger age group is 55 minutes less than for Ron's —- it was crushing. Ron ran last year's Boston Marathon alone (in 4:10:26).

The younger Mastin finally qualified for Boston last May at a marathon in Nebraska. When he crossed the line there and saw the time was good enough, "I had this huge rush of emotion. I started crying, so hard that a volunteer came up to ask me if I was all right," he said. "It set the dream in motion."

The son had earned one more chance to know his father. They never would have the memories of playing catch or sitting cross-legged at an Indian Guides meeting. But it wasn't too late. They would have Boston.

Monday filled the pages of a spotty family album. They'll remember Michael hamming it up in his Kansas Jayhawks shirt, weaving from curb to curb high-fiving spectators along the route.

They'll remember a cool, sunny day that fooled Ron into going out a little faster than planned. By mile 13, he began to have doubts about finishing. But stopping was not an option.

There was the "screech tunnel" of Wellesley College, an all-female cordon of deafening encouragement for all who run. There was "Heartbreak Hill," hardly the toughest obstacle Ron has beaten. And then, the glorious half-mile, downhill ramp to the finish, when father and son drew close and coasted in.

"The best part about running with Dad [and running slower] was that I wasn't worried about my time. I just got to enjoy the scene, to soak everything in and what it meant," Michael said.

This was a meaningful milepost in the Mastins' marathon, but hardly the end. They just stopped running for a while to catch their breath.