Update: I just reached Scott Menzies in his hotel room. He was amazed by the crowds -- "five deep almost the entire way through" -- and the energy along the route from Hopkinton to Boston. Supporters were so loud he often couldn't hear his music, a selection of tunes that he and Meg used to listen to while dating, he said.

He said he wore Meg's 2012 Boston Marathon bib (the paper with her assigned number) beneath his shirt. "I thought about her a lot. I felt her on the hills. I kept hearing her say 'push, keep on pushing,'" he said.

He said he was strong until about mile 23, when his legs began to tire. Over the last mile he slowed intentionally, to savor the experience. "I was doing this for her and really didn't have a chance to think about anything else," he said. "It was an emotional time."

Update: The Meg's Miles Facebook page says Scott Menzies finished the marathon in 3:51:57, a pace of 8:50 per mile. I'm trying to reach him on his cellphone.

Original Post: Meg and Scott Menzies were a mile into their training run on that cold January morning in Ashland, Va., three months ago. It was their Monday morning "date," Scott Menzies said, a way to spend time together after their three children had gone to school for the day.

Meg, 34, a stay-at-home mom from Hanover, outside Richmond, was training to run the Boston Marathon again and, though she was too humble to tell many people, had her eye on a spot at the U.S. Olympic trials. Scott, also 34, an Ashland police sergeant, just tried to hang on during the eight-mile runs with his speedy wife.

The school bus had been a half-hour late. They should have been farther along their route. They were running single file against traffic, the way you're supposed to, with Scott first and Meg right behind him. Around 8:15 a.m., a Toyota Sequoia driven by Michael Carlson, a physician who was allegedly drunk, veered off the road while rounding a curve. Scott was able to jump out of the way. Meg was not. She was struck and declared dead two hours later.

Today, Scott Menzies will run the Boston Marathon in his wife's place with the support of tens of thousands of runners and others around the world who have rallied around him through an extraordinary Facebook group called Meg's Miles.

"The only reason I want to do it is because that's what she was doing," Scott Menzies told me Friday. "She was training, and I want to finish it for her. And it’s kind of a selfish thing for me, but that’s where she would be. I want to see what she would see."

In 2004, Carlson lost his wife in a head-on collision near Buffalo. He is also battling leukemia, according to local media reports. He is raising the couple's three children and his wife's two children from a previous marriage. He received a $7.7 million settlement in a court case that followed the accident.

Carlson's blood alcohol registered .11 in the accident that killed Meg Menzies, above the legal limit of .08, according to court documents cited in various media reports.

Scott Menzies said his family is devoutly Christian, and his wife adored raising their two sons, 9-year-old Gabriel and 7-year-old Whitfield, and a daughter, Skye, aged 5. "We’re a simple Christian family and would consider our family an average family," he said. They lived paycheck to paycheck, he said, so Meg could be home with the children and volunteer at Cool Springs Baptist Church. Part of Scott Menzies's job was to give presentations on the perils of drunk driving.

He said his family is doing "as well as could be expected. My children get upset every night. They miss her. The nights are tough, and then there are questions in the daytime that I just don’t know how to answer. You don’t really prepare for this."

A woman whom Meg Menzies had met through her daughter's playdates, Brooke Roney, started a Facebook event after Meg was killed, hoping that a few thousand local people would dedicate their runs to Meg the following Saturday, Jan. 19. Instead, more than 99,000 people around the world ran, Roney said. "I created a Facebook event and encouraged everybody to dedicate their miles to Meg and to enjoy the surroundings, rain or shine, and just feel blessed to be able to run. Because some people can’t."

The event became a Facebook group that has more than 16,000 members, many of whom have continued training in Meg Menzies's honor. They post messages describing how her memory keeps them going. "Meg’s story inspired a lot of people to get up, get moving and get healthy," Roney said.

Scott Menzies said the worldwide outpouring of support for him and his family has been "a form of therapy."

"I don’t think there’s any way anybody can deny there’s a God," he said. "... She wasn’t famous. She wasn't a rock star.  For the world to react to a simple, average Christian mom ... I never would have expected it. She never would have wanted it. She’s very humble."

With special permission from the Boston Athletic Association, Scott Menzies will toe the starting line in Hopkinton in a few hours, remembering his wife as the running world pays its respects to the three people killed and more than 260 injured in last year's terrorist attack.

"It's to honor her and to finish what she started," he said. "But I just want to see what she would have seen."