When ISIL took control of Mosul in June 2014, it was intent on consolidating a stunning victory over Iraq's security forces by rooting out resistance with its trademark brutality.
Crammed on to flatbed lorries and buses, thousands of men with their hands tied behind their backs were driven out of the city and to their deaths by Abu Bakr Al Baghdadi's killers.
Lined up at the edge of a sinkhole, locally known as Khasfa, they were shot and their bodies dumped into the ditch, never to be seen again.
Policemen and soldiers were hunted down and brought to Khasfa, along with tribal leaders and village elders opposed to the terrorist group.
Soon, a steady stream of pick-up trucks and minibuses travelled the rugged desert between Mosul and the sinkhole.
According to Human Rights Watch the ditch could hold up to 4,000 bodies, making it the site of the biggest mass murder committed by ISIL, dwarfing the infamous massacre at Camp Speicher near Tikrit, where up to 1,700 bodies were found.
The site is rumoured to have been used by Al Qaeda to dispose of bodies in the bloody years following the 2003 US invasion. Earlier, it may even have been used by Saddam Hussein to rid himself of his enemies.
ISIL wasted little time in following suit.
"I saw it with my own eyes. They bought people from Mosul or Qayarrah," said Yaser Ahmed, a forty year old resident of Kharbat ibn Qwan, a nearby village that lines the main road running out of western Mosul. "I was herding sheep, and I saw Daesh shoot them with pistols and machine guns."
The killing at Khasfa was relentless. Seeking to instil fear in the local population, the extremists wanted their crimes to be known.
"They weren't hiding it. Sometimes they told people to come and witness the killings," said Mr Ahmed.
Walid Hassan, a 27 year old from the Wadi Hajjar neighbourhood of West Mosul, travelled regularly to Khasfa to buy petrol and often saw vehicles filled with men being driven towards the sinkhole. He did not need to bear witness to the killings to know what happened next.
"We saw the Khasfa killings on video. Daesh showed them on a big screen in a roundabout in Wadi Hajjar. You could also buy them on DVDs in the neighbourhood," he told The National.
In 2016 the killings at Khasfa stopped — ISIL dumped shipping containers, car wrecks and earth on to the pile of corpses, so covering up the murder scene.
To prevent the unearthing of the grave ISIL laced the area around the hole with explosive booby traps. The terror group continued to kill its opponents but the bodies were no longer dumped into the hole.
In February 2017 Khasfa was found by local forces as they advanced towards Mosul in their quest to liberate Iraq's second city. Since then, however, the government has made no move to reveal the sinkhole's grim secrets.
According to the International Commission on Missing Persons (ICMP), an organisation that assists in the excavation of mass graves, the government has yet to set up a database of people who are presumed to have been killed by ISIL in Mosul, making it impossible to identify the bodies in the grave. Without this preparatory work, there is little point in exhuming the corpses, experts say.
"What would be the benefit of going in here?" asks Caroline Barker of the ICMP in Iraq. "It's massively expensive and an awful lot of initial work has to be done."
But without definite proof of death, many families are unwilling to accept that their loved ones have gone forever.
In the Karama neighbourhood in east Mosul, 59-year-old Younis Mohammed sits on a cheap sofa in the courtyard of a modest house and produces a folded piece of paper from his wallet with shaky hands. It is a death certificate issued by ISIL, declaring that his daughter Naima was murdered by the terror group late in 2016 on suspicion of passing on information to the Iraqi military by phone.
Mr Mohammed, a frail old man with a worried demeanour, visited the headquarters of Amnyah — ISIL's secret police — on numerous occasions, desperate for information on his daughter's fate. But the extremists refused to hand over her body. Today, Mr Mohammed continues clinging on to hope. "We are still not sure if Naima is really dead," he says.
ISIL, posits the elderly father, often did not kill the people they whisked away. Instead they kept the captives alive in the Amnyah headquarters in the Al Jamhurri hospital, where they were found by the liberating Iraqi troops in June last year.
Desperate relatives such as Mr Muhammed believe that, rather than being released, thousands of captives were transferred to prisons in Baghdad.
"It is very common that people who were taken prisoners by Deash were [later] taken by the [Iraqi] security forces. They are now in Baghdad, they are in Muthanna airport," said Mr Muhammed.
What may sound like a wild conspiracy theory to outsiders is seen as an established truth by many families of ISIL victims, who believe their relatives are kept in Muthanna airbase or Taji prison — notorious detention sites in Iraq.
On Facebook, images purportedly showing Iraqi soldiers snapping selfies in front of men found in an ISIL jail have found their way on to the smartphones of those searching for answers.
Willing to put hope above reason but lacking in organisation, the relatives of the Mosul missing have become easy prey for politicians seeking to exploit their plight in the upcoming national elections in May.
Many praise Salim Al Jabouri, speaker of the Iraqi parliament, and Saed Zaedan, a parliamentary candidate and political ally of Mr Jabouri, for taking on their cause.
They are "the only people helping us", insists Mr Muhammed. "They are trying as hard as they can."
Mr Zaedan has been compiling lists of families who have lost relatives to ISIL in Mosul and says his efforts have been acknowledged by government officials. He is quick to draw attention to his activism on social media and the local press. He is also keen to fan the flames of mistrust towards Baghdad.
"At the time of the liberation of Mosul, a lot of people were freed from ISIL prisons. But afterwards these people vanished," he told The National. Mr Zaedan is also candid about his electoral ambitions.
"Of course these people will appreciate what we have done, and it will lead these families to give me their votes," he said.
But not everyone agrees.
"All these people just want to know what happened to their relatives. They want hope or at least results. These MPs and candidates are taking advantage of the people in this matter," says another Mr Mohammed, an elderly man whose son Farhard was detained by ISIL in 2016 and has been missing since.
Mr Mohammed also believes that his son was taken to Baghdad by security forces after the liberation of Mosul. He has paid prison officials $20,000 (Dh73,450) for unreliable proof of life, in a desperate battle to find his missing son.
Like so many family members in Iraq — ICMP estimates that up to one million people are missing from decades of conflict. Mr Mohammed continues clinging on to hope, although he has given up on people such as Mr Al Jubouri and Mr Zeadan.
"They are saying that they will help, in reality they are doing nothing," he says.
The end of ISIL may have marked the creeping rebirth of Iraq, with cities such as Mosul and Fallujah returning to life. But amid the resurgence, government inaction about identifying the victims of ISIL's three years of terror and atrocities has left thousands of families in painful uncertainty over the fate of their loved ones.