When Christopher Dempsey offered to donate half his liver to a complete stranger, he knew it would be a life-changing experience.
What the former marine didn't know was that he would be saving the life of the woman who would become his wife.
But less than two years after Mr Dempsey called Heather Krueger to reveal he was a match, the two were married.
The love story began with a conversation overheard in a workplace break room in Frankfort, a village south of Chicago, Illinois.
Miss Krueger had stage four liver disease, and had been ill for about two years already when doctors told her she only had a 50% chance of surviving another two months without a transplant.
Her family were in a race against time to find her a donor - a hugely difficult task in a country with more than 119,000 people on its transplant waiting lists.
That was where code enforcement officer Mr Dempsey came in.
"I heard a co-worker talking about his cousin who needed a liver transplant," Mr Dempsey told the BBC.
"I just thought to myself, I would want someone to help me or my family in that situation."
The 38-year-old decided to get himself tested and discovered he was a match for the then Miss Krueger, now 27.
The first time they spoke was the moment he called to tell her he would be her donor at the start of February 2015. Later, she would tell him how she and her mother had cried tears of joy after receiving the call.
They first met shortly afterwards when Mr Dempsey took Miss Krueger for lunch - and he paid.
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In the weeks leading up to the transplant, they began to spend increasing amounts of time together as Mr Dempsey and his motorcycle club threw themselves into fundraising.
"We were going out looking for donations for a benefit, and I just started thinking, she's a really nice girl, she is somebody I would like to get to know."
By the time of the surgery at the University Of Illinois Hospital on March 16, they had already been on a couple of dates, but they only made it official afterwards.
"I was really confident everything was going to be okay," said Mr Dempsey. "I was still nervous - there is always the chance [something might go wrong] - but at no point did I rethink the decision.
"It was just really good knowing she was going to be okay."
The proposal came eight months later, after a horse and carriage ride in Chicago. Then, almost 19 months to the day of the transplant, the healthy couple became Mr and Mrs Dempsey.
"I think it was definitely more emotional - maybe more so for her and her parents - knowing what we had both been through," said Mr Dempsey.
"I never would have thought in a million years when I agreed to all this that I would marry her. It is amazing."