Kevin Garratt remembers well the night he and Julia were arrested in north-eastern China.
He recalls being pulled away from his wife as they walked through a restaurant's downstairs lobby, and pushed into the back of a black sedan filled with burly officers.
He thought the whole thing was some terrible mistake.
Julia, forced into a separate sedan, found herself shaking in fear and shock at the sudden turn of events, and the drive in the darkness.
She thought: "This is going to be my last night.
"I don't think I've ever felt that level of fear and panic before. And also just sad for my family and my children, because there was no warning, there would be no chance to say goodbye."
The Garratts had lived in China since 1984, and from 2008 operated a coffee house popular with Western expats and tourists in Dandong, a city on the North Korean border, while continuing to carry out Christian aid work.
But unbeknownst to either of them, early in 2014 and thousands of miles away, American authorities were launching a crackdown on Chinese cyber-espionage. One of the men in their sights was Su Bin, a Chinese resident working in Canada.
That June, Canadian authorities picked up Su, accused of stealing data about military projects and selling it to China, for extradition to the US.
While China has denied it, Canadian officials and observers believed the Garratts' arrest was a tit-for-tat detention and an attempt to pressure Canada for Su's release.
Canada's ambassador in Beijing at the time, Guy Saint-Jacques, describes them as "a couple of Canadian missionaries who had been in China 30 years doing good work".
He tells the BBC their arrest "was the first case where we saw a clear retaliation for something that had happened in Canada".
When he met counterparts at the foreign ministry about the case, Saint-Jacques recalls: "They never said directly 'let's do a swap.' But it was very clear what they wanted."
On the night of the Garratts' arrest - the beginning of months of detention for the pair - they had been invited for dinner by a friend of a friend, who told the couple they wanted to talk about their daughter going to study in Canada.
But something about the dinner felt strange.
"It didn't seem genuine, and the daughter never came," Kevin says.
Julia says it was only later they realised the whole evening had been a set-up for their arrest.
"It was very carefully thought through and planned in advance. We had no idea," she says.
