|NFL International Series: Detroit Lions v Kansas City Chiefs|
|Venue: Wembley Stadium Date: Sunday, 1 November Kick-off: 14:30 GMT|
|Coverage: Live on the Red Button and BBC Sport website; highlights on BBC Two at 00:15 GMT on 2 November|
Take Cairo Santos, a 23-year-old kicker for the Kansas City Chiefs in the NFL. Hit the rewind button on his life and go back eight years.
Rewind until his square shoulders turn skinny and his confident demeanour shades into shyness. When you get to the part where this elite sportsman is just a nervous 15-year-old exchange student, kicking a football on a Florida driveway while the other kids play basketball, stop. You've arrived at the moment his life changes forever.
It was Tyler Burnett, his exchange partner, who saw the young Brazilian's football prowess and asked him to see if he could kick an American football down the street. Tyler got on his belly and held the ball out.
"I took two steps back and just hit it as hard as I could," Santos says.
The contact was sweet, and the ball flew, "low, kind of like a soccer kick". It travelled far, 50 yards or more. The direction was straight and true. And the direction of Santos' life was altered more wildly than he could have imagined.
"When I look back on that moment, it makes me smile," Santos recalls. "Right there was a huge turn in my life. It was an introduction to something that I fell in love with."
|What does a kicker do?|
|A kicker is responsible for kicking a team's field goals and extra points|
|They only enter the field for the kicking plays, as part of the special teams unit|
|They are often among the smallest and lowest-paid starters on an NFL team|
|But they are usually the highest-scoring players: the 25 top points scorers in NFL history are all kickers|
If Santos had scuffed that kick, he might never have discovered American football. He would not be playing at Wembley Stadium in Sunday's International Series against the Detroit Lions. The NFL would still be waiting for its first Brazilian player. And the Burnetts, a regular family from St Augustine in the Florida suburbs, would never have gained a second son.
This is Cairo's story of travel, tragedy and triumph.
'I dreamed of playing football for Brazil'
Cairo Santos grew up in Brasilia. His childhood was typical of Brazil. First came his family: mother Magalie, father Cairo Sr - a commercial pilot who became a stuntman - and his sister Talita. And after that, a close second, came football.
"I was so obsessed with soccer," he remembers. "I dreamed of playing for Brazil one day, wearing that jersey.
"Every time Brazil played in Brasilia, I went to the games. I would buy every year's jersey for Flamengo, for Brazil, and even for Chelsea."
Santos wanted to be a midfielder, like his favourite player Ronaldinho. But he had a problem. In Brazil, it is hard for an aspiring young footballer to stand out. So when he was 15, he decided to go to the United States for a year.
"Brazil is so competitive and difficult to make it," Santos says. "So my plan was to study here, learn the language and also figure out if I could stay here and play soccer in the US."
In this plan, there was no place for the strange American game which Santos had occasionally glimpsed on television, in which huge men in helmets and shoulder pads brutally smashed into each other.
"I had no intention of playing it," Santos remembers. "I was never a big guy, so I wanted to stay away from that because I didn't want to get hurt. My focus was on soccer."
Learning gridiron on a games console
Even after that moment of epiphany on the driveway, Santos took some convincing. He still wanted to play for the high school soccer team. It was only after his friends assured him that the kicker enters the field exclusively for the kicking plays, without getting tackled, that he agreed to try out for the American football team.
His exceptional talent for the sport quickly became obvious. Within days, he was on the high school team. Within weeks, the teenager was knocking over field goals from 54 and 57 yards - distances that would test a seasoned NFL kicker to their limit.
For a kid who had only ever known football, donning a helmet and kicking an oval ball was strange. The weird lexicon of positions and playcalls was confusing to ears that had yet to master English. But Santos thrived on the responsibility.
"It felt a lot like kicking a free-kick or a penalty kick in soccer - scoring a point, helping your team win," he says. "I loved everything about it."
|Famous foreign NFL players|
|Sebastian Janikowski (Oakland Raiders): The Polish kicker holds the record for the most 40+ yard, 50+ yard and 60+ yard NFL field goals|
|Tamba Hali (Kansas City Chiefs): The five-time Pro Bowl linebacker was born in Liberia|
|Lawrence Okoye (Arizona Cardinals): Former GB Olympic discus thrower who now plies his trade as a defensive end|
|Sebastian Vollmer (New England Patriots): Born in Dusseldorf, Germany, offensive tackle Vollmer won the Super Bowl with the Patriots last season|
Inspired, he taught himself the rules by playing video games in his spare time. Suddenly, the images of virtual gridiron on the screen seemed more vivid than the faded pictures of soccer glory which had adorned his childhood bedroom. Sitting in a living room in Florida, the American dream felt a lot closer than the Brazilian fantasy of playing for the Selecao.
"It was very tough," he remembers. "Soccer was a huge part of my life. But I just wanted to be a professional athlete: that was my goal, the only thing that I could see myself being."
And so Santos decided to do what no-one from his country of 200 million people had ever done before.
'They loved me like their own family'
David and Kathy Burnett did not even sign up to the school's student exchange programme. They only took Santos because of a chance phone call: the school had one Brazilian student for whom they could not find a host family.
"It's kind of a shocking experience at first: stepping into the house of these people who you don't know," Santos says. "There's that pressure of 'Are we going to like each other? Am I going to understand them?' My English wasn't good, and it took me about two months to settle in and feel comfortable."
But when the nervous, polite Brazilian kid who they had expected to be part of their life for a matter of months told them that he intended to stay in the US, the Burnetts did something extraordinary.
"They took me in and loved me as one of their own family," Santos says. "I was so blessed to connect with them in the way I did.
"I never had a brother in Brazil, but in Tyler I have a brother. We connected like we had known each other forever. We fit into each other's lives perfectly."
The Burnetts' spare room became Santos' room, and his ambitions became theirs.
"When I started to kick and play for the high school team, I wanted to train and get better, and I found a coach about an hour away who wanted to train on Sundays," Santos explains.
"So my host mum would drive me every Sunday, an hour there and an hour back. That's something that I would expect my actual mum to do, not somebody who's taken in a foreign student. They really were like parents to me."
'The toughest experience of my life'
Santos continued to excel in American football. He won a scholarship to Tulane University in Louisiana, a school in the top division of American college football. He finished his college career with the best field goal percentage in Tulane's history, and in 2012 he won the Lou Groza Award for the nation's best collegiate kicker.
Then in September 2013 came the worst day of Santos' life.
His mother called late one Sunday evening. 4,500 miles away, his father had been killed in an accident in his stunt plane.
"It was the toughest experience I've ever had," Santos remembers. "My body was here, but my mind was in Brazil.
"I wanted to be with my family but I knew I had to continue to play here - that's what my dad would have wanted."
So Santos kept kicking. He concentrated his gaze on those two narrow posts and blocked out everything around them. And the Burnetts, who had reckoned on driving Santos places and making faltering conversation for a few weeks, found themselves holding a young man's world up.
"When I came back to the US after my dad's funeral, they wanted to comfort me and be there for me," Santos says.
"I'm so thankful to have two families. Since I lost my dad, Dave has been that guy for me."
Coming full circle
Santos made it. He won a place on an NFL roster. Last season, he kicked the most points by a rookie in Chiefs history. This season, he kicked seven field goals in a game, the second most ever in the NFL.
His gamble to abandon his football ambitions paid off. But on Sunday, he will get a small taste of his childhood dream.
"Playing at Wembley for me is incredible because of all the memories I have of watching Chelsea and England," he says.
"I was so happy when they told us that we were going to have a game here. I've watched so many games on TV that I have a great idea of what it looks like: the atmosphere, the stands, the grass. I can't wait to experience it in person."
If Santos kicks a field goal at Wembley, he will point to the skies, just like he does after every kick.
"Every time I'm on the field, it's for my father, it's to remember him," he says.
"That's the thing that always hurts a little bit inside. But I'm doing what I love and I know he's watching me.
"I didn't get here alone. So that's what I play for: for my family, for my dad, for all the people who have been there for me."