On her way to becoming the first American winner of the Boston Marathon in 33 years, Desiree Linden stunned onlookers with a selfless act of sportsmanship.
Linden, 34, said she felt early on as if she would not be able to finish the 42 kilometre race, but even despite that struggle she was happy to sacrifice crucial time for her compatriot Shalane Flanagan.
Only a few kilometres into the race, Flanagan had to drop out of her lead position for an an emergency toilet stop.
Commentators were stunned that the race leader would sacrifice her position, but were then even more surprised by Linden's selfless reaction.
The eventual marathon winner slowed the pace right down, losing a couple of hundred metres, to rejoin her good friend, before encouraging and supporting her push to get back to the lead pack.
The great act of sportsmanship turned out being a blessing in disguise for Linden, who found herself boosted by working to help the reigning New York Marathon champion.
Making, the selfless act even more impressive, Linden had lost the 2011 race by just two seconds.
"At mile 2-3-4 I didn't even feel like I could make it to the finish line," Linden said after her victory.
"I told her (Flanagan) anything I can do to help you let me know because I might drop out.
"Helping her helped me and I got my legs back from there."
Watch the incident play out in the video at the top of the page.
Good deed rewarded
Linden overtook Ethiopia's Mamitu Daska and Kenya's Gladys Chesir at Heartbreak Hill after the 32km mark and kept the lead from there to win in 2:39:54. American Sarah Sellers was a distant second in 2:44:04 with Canada's Krista Duchene third, another 16 seconds adrift.
No US woman had won the Boston crown since Lisa Larsen Weidenbach 33 years ago, but Linden did it in the sixth Boston start of her 16 marathons.
"I love this city, this race, this course. It's storybook. I'm thrilled to be here and to get it done," Linden said.
"This is a race the entire city cares about. Even on a day like today when it's pretty miserable, the people show up and embrace the race."
Linden lost by only two seconds in 2011 and was fourth in 2015 and 2017.
The race marked five years since the Boston Marathon bombing tragedy in which two explosions near the finish line killed three people and wounded more than 260.
Elite competitors began in rain coverings and at a slow pace in the coldest start since 1988 at 38 degrees (3.3 Celsius) with rain often blowing into runners' faces.
Weather conditions were so bad the Boston Red Sox, who usually play a Major League Baseball home game on race day, postponed their Fenway Park contest for the first time since 1984.
Meanwhile, Yuki Kawauchi became the first Japanese man in 31 years to win the Boston Marathon on Monday with his fourth marathon triumph of the year.
Kawauchi overtook defending champion Geoffrey Kirui of Kenya over the final two kilometers in heavy rain to win in 2hrs 15min 58sec with Kirui finishing in 2:18:23 and American Shadrack Biwott 12sec further back in third.
"This is the greatest day of my life," a tearful Kawauchi added. "This is Boston. This is the greatest race in the world."