Warning: Contains images some may find upsetting
A computer scientist at a university in the north of England is studying an image of a corpse - attempting to solve a mystery that has gripped the Middle East for nearly 50 years.
This is what he looks like now? asks Bradford University's Prof Hassan Ugail doubtfully.
The digitised photo is of a decomposed face and is about to be run through a special algorithm for our BBC investigation.
The original photo was taken by a journalist who saw the body in a secret mortuary in the Libyan capital in 2011. He was told then that it could be charismatic cleric Musa al-Sadr, who vanished in Libya in 1978.
Sadr's disappearance has spawned endless conspiracy theories. Some people believe he was killed, while others claim he is still alive and being held somewhere in Libya.
For his ardent followers, his disappearance holds the same level of intrigue as the 1963 killing of US President John F Kennedy. Such is the sensitivity of our long investigation that my BBC World Service team and I even found ourselves detained in Libya for several days.
Emotions run high because Sadr is so revered by his followers - both for his political reputation, having advocated on behalf of his native Lebanon's then-marginalised Shia Muslims, and as a wider religious leader.
His followers gave him the title of imam, an unusual honour for a living Shia cleric and one bestowed on him in recognition of his work on behalf of the Shia community.
His mysterious disappearance has added to his emotional power because it echoes the fate - according to the largest branch of Shia Islam, known as Twelvers - of the hidden 12th imam, who disappeared in the 9th Century. Twelver Muslims believe the 12th imam did not die and will return at the end of time to bring justice to Earth.
And Sadr's disappearance also arguably changed the fate of the world's most politically, religiously, and ethnically volatile region - the Middle East. Some believe the Iranian-Lebanese cleric was on the verge of using his influence to take Iran - and, as a result, the region - in a more moderate direction when he disappeared on the eve of the Iranian revolution.
So there was a lot riding on Bradford University's identification efforts. The journalist who took the photo told us the body was unusually tall - and Sadr was said to be 1.98m (6ft 5in). But the face had barely any identifiable features.
Could we finally solve the mystery?
We were on the second day of our deployment in Tripoli, looking for the secret mortuary. Kassem, who was accompanying the BBC team, couldn't remember the name of the area he had visited in 2011, except that it had been near a hospital.
We were told there was a hospital within walking distance and headed off to find it.
Suddenly, Kassem said: This is it. I'm sure of it. This is the building that contained the morgue.
It was disturbing to feel we had become part of the story. Libya is still divided into two rival administrations with competing militia, and staff at the prison had indicated Libyan intelligence was being run by former Gaddafi loyalists who would not want the BBC investigating Sadr's disappearance.
Some people have long believed Sadr was murdered. If Gaddafi did order Sadr's killing, then why?
Many questions remain. But during our investigation, the quest for answers continues as we seek to understand the fate of a figure who remains a powerful symbol for many.
