Sky News can reveal that a group of men arrested in Denmark two weeks ago were all named in Islamic State recruitment files leaked to us in March.
The link between the arrests and the files also exposes a connection between Danish IS recruiters and British extremists.
Two days earlier, a 20-year-old man was arrested at the city's airport. It is understood he was trying to board a plane with a large quantity of cash.
In total, five people were detained and a further four "detained in absentia". Their whereabouts are not known.
However, authorities refused to give many further details. In a so-called "double-locked door" legal hearing, the media were prevented from publishing the names of the men.
But Sky News has seen their names and those of the men still being sought. All appear in files leaked to Sky by a disillusioned IS member in March.
Filled out by IS gate keepers when recruits entered the self-proclaimed caliphate, the files are now exposing fighters who have slipped back into their home countries.
One by one authorities are picking them up and piecing together a terror franchise that spans the continent.
We rang the doorbell at the address of one of the detained men.
His entry form lists him as married. He lists his occupation as "childcare" and it states that he entered IS territory on 1 July 2013. It is not clear when he returned to Denmark.
A neighbour told us she knew the man well.
"I would say hello to him every time I walk in or out of the door. A really nice guy, very helpful. He offers to drive me so I don't have to take a cab," Lise-Lotte Christensen said.
We showed her the man's file. "It really surprises me. I had no idea he was that kind of guy, he was just really nice. A lovely, warm person," she said.
She confirmed to us that he has two young children and a Danish wife, all information which tallies with the associated file.
As with all the files, it lists the person who recommended the man's entry to IS. In his case it was an individual called Abu Hifs Al Pakistani, one of two names which crops up frequently in the files.
Across town, we visit another neighbourhood and the scene of another raid.
One man was taken from a second floor apartment in a block. The name on the doorbell is the same as that on the file which lists further details.
Born 1990, married, entered IS - 9 September 2013, recruiter - Abu Khatab al Pakstani. His name is the other which appears in a number of the files.
The form of the man arrested at the airport details him as a 20-year-old former mobile phone technician who travelled to Syria on 10 July 2013 when he'd have been just seventeen.
A well-known Copenhagen mosque is listed as his home address.
We know the man was close to the mosque's imam. We were told the imam was away in Mecca and our calls to his mobile phone didn't connect.
The recruit's sponsor is, once again, Abu Hifs al Pakistani.
Between them, Abu Hifs and Abu Khatab are named as the recruiters in all but three of the Danish files.
We have obtained footage of Abu Khatab at a rally in Copenhagen in late 2012. The IS files show us that he would have been recruiting people for jihad at this time.
In the footage, he is seen plugging a mobile phone into a loudspeaker.
On the other end of the line is the radical cleric Omar Bakri Mohammed, who was once based in Britain and whose connections to radical groups in the UK remain strong.
YouTube footage shows Abu Khatab alongside Abu Hifs in Syria in 2013.
Both men are now dead, but both had contact with known British extremists like Bakri Mohammed and another who can't currently be named for legal reasons.
The two men's exposure as high profile recruiters helps European intelligence agencies join up the dots.
A former analyst at the Danish Intelligence Service says that highlighting patterns in the forms is crucial in helping to understand IS.
"One of the most interesting things in the files is who recommended the recruits," Anja Dalgaard-Neilsen said.
Ms Dalgaard-Neilsen is now the director of the Institute for Strategy at the Royal Danish Defence College. She says the files help not only to apprehend suspects but to prosecute them.
"It has now been criminalised to join a terrorist organisation and that's the reason why these files are potentially very interesting to the authorities, because they could support the argument of the authorities of the prosecution that these people joined a terrorist organisation," she said.
"It is, for obvious reasons, difficult to gather evidence in a war zone.
"Until recently it wasn't a crime in and of itself to travel to Syria so you couldn't know if people were doing humanitarian work or whether they had actually joined a terrorist organisation."
The challenge for the authorities is identifying all those in the files.
There are many more Europeans named in files than there have been arrests. Some individuals may have died in Syria. But others could have travelled back to their home countries.
After the atrocities in Paris and Brussels, and IS' pledge to attack again, there is an urgency to find them.
