In an opulent, abandoned apartment within Syria's capital, Damascus, armed individuals in military attire meticulously searched through designer apparel and documents.

Dozens of photographs of a slender man in various settings—at his desk, even playing in the snow—were strewn across the living room floor, beneath a gleaming crystal chandelier. Multiple copies of one image showed him warmly smiling while shaking hands with the deposed dictator, Bashar al-Assad.

The man wasn't immediately recognizable, but nearby gold medals and gilded certificates bore the name Hussam Luka.

Known as "The Spider," Luka was a key enforcer for Assad, accused of orchestrating atrocities and systematic torture, leading to sanctions from the UK, US, and European Union.

As the head of Syria's most potent civilian intelligence agency, Luka was among the nation's most feared figures, yet much of his work was conducted covertly.

Like other regime members, Luka seemingly vanished overnight in December 2024 following Assad's overthrow, leaving behind unanswered questions and demands for justice that many fear will remain unfulfilled.

Days after Assad's fall, we observed rebels in Luka's apartment, searching for clues about his whereabouts.

In a living room corner, on a console table, lay an unassuming notebook.

Inside, scrawled in blue ink, were dozens of names—from shopkeepers and doctors to military officials and individuals sharing the Luka family name.

Could these contacts provide insight into "The Spider" and his crimes, or even help us locate him?

At one point, Luka's own phone number was widely known; in the early days of the Syrian civil war, it was spray-painted on walls in the central city of Homs.

The conflict began with Assad's brutal suppression of a pro-democracy uprising in 2011, a war that would claim hundreds of thousands of lives.

Luka, a local head of the Political Security Directorate, one of Assad's primary intelligence agencies, was tasked with reclaiming Homs from rebels.

At the time, rebel-held areas in Homs were under government siege, and residents struggled to access food and medicine. Several individuals, including former rebel fighter Motaz al-Zaydi, recounted resorting to eating rats.

Al-Zaydi recalled Luka's name and number appearing on a neighborhood wall, and the message spread that those wishing to escape the fighting could call for safe passage.

While some are believed to have been granted safe transit out of the city by Luka, others who called were never seen or heard from again, according to several people interviewed, including al-Zaydi.

Many referred to Luka as "The Spider" due to his extensive network of allies and informants, some embedded within rebel groups. "He was everywhere," Homs residents told us. Al-Zaydi described Luka as an "evil genius" and "a fox of a man."

However, his most egregious action in the city, many argue, was his alleged involvement in the "Eid Massacre," also known as the "Children's Massacre," which the US cited when sanctioning him.

It was the Muslim holiday of Eid al-Adha in September 2015, and Mohammed Towakatli's seven-year-old son, Wael, was gardening in the playground he had created in the al-Waer neighborhood.

At 17:10, just after the power ration began, Mohammed remembered the strike hitting.

Walking through the park earlier this year, now planted with rows of saplings, Mohammed recalled the names of the children killed and the games they were playing, gesturing to where he found their bodies, including Wael's.

"They were tiny children," he said with tears in his eyes. "The ground here was painted red with blood."

Twenty-eight people were killed, including 17 children and four women, according to the Syrian Network for Human Rights.

Luka, according to a Syrian activist group and a pro-opposition newspaper at the time, was responsible for the regime's target selection in the area that day.

His actions in Homs earned him a promotion, and by the regime's collapse, he led the General Security Directorate (GSD) intelligence agency, making him one of the country's most powerful figures.

Government security services could target anyone—from opposition fighters, journalists, doctors, or rights activists, to individuals perceived as opposing the Assad government in any form.

Those arrested were held in Syria's political prisons, including Sednaya in Damascus—a facility so infamous it was dubbed the "human slaughterhouse." Many imprisoned there were never seen again.

As head of the GSD, Luka had strategic control over Syria's detention policies, and his personnel monitored communications to and from Sednaya.

Across Syrian society, there are widespread calls on social media for former senior officials to be held accountable. Some also contend that the new Syrian government is not doing enough to bring these individuals to justice.

Syria's Attorney General, Hassan al-Turba, informed the BBC that the government had initiated a lawsuit against Luka, accusing him of "premeditated murder, torture, and death resulting from torture."

"A warrant has been circulated domestically, and we are working on circulating it internationally as well," he stated, adding that the administration was working to track the location and seek the extradition of Luka and other missing senior regime officials.

As he continues to mourn his son, Mohammed told the BBC he desired Luka, along with other senior regime officials, to be returned to Syria and executed.

"They look like humans but have no humanity in them at all," he said.

We had photographed every page of the book found in Luka's apartment and, back in London, began testing all 155 numbers—aware that many close to the regime would have fled or gone into hiding. Fifty-one numbers appeared operational.

We then re-called these in order of their apparent importance to Luka, starting with military commanders and relatives.

Every call was unsuccessful. Anyone who answered simply hung up when we explained who we were and what we wanted—or denied knowing Luka or his family, or even being the people listed in the book.

Consequently, a BBC reporter, whose own name was once on a GSD wanted list while Luka ran the agency, traveled to Syria to try in person.

Many listed in the phone book were doctors, so our reporter began booking medical appointments with some of them as a way to meet them.

A doctor in Aleppo reluctantly admitted treating Luka but then ordered our journalist to leave and returned his consultation fee.

Our reporter then booked an appointment with another doctor from the phone book, this time based in Damascus. This doctor revealed he had once accompanied Luka's mother on a medical trip to Russia but was reluctant to provide more information, vaguely directing us to a pharmacy belonging to one of Luka's daughters.

Locals said she, too, had not been seen since December 2024.

For months, our hunt for Luka yielded no results.

Then, we had our first breakthrough.

One of those listed in the book, whom we tried calling again, finally answered the phone.

He had been the guard for Luka's apartment block, he told us, and eventually agreed to provide the number for someone he said had been Luka's personal bodyguard—a man we are calling Mahmoud.

It took weeks to secure an interview with Mahmoud. Meetings were scheduled but he wouldn't appear, or he would request a meeting in a private space such as a car or apartment, which our reporter deemed too risky.

They eventually met at a hotel one night, just before midnight. Broad-shouldered and physically imposing, Mahmoud seemed to carefully consider each answer before speaking.

He told us he was angry with Luka for abandoning him when the regime fell. As word spread in December 2024 that Assad's rule was on the brink of collapse—with rebels advancing on the capital—Luka had said he would stay and defend Damascus, Mahmoud told us. But by the early hours of the next morning, Luka had disappeared, taking a large sum of money from the office safe, Mahmoud said.

Mahmoud refused to share any contact details for Luka or his family but did give us a number for Luka's driver, whom he believed had driven the former spy chief out of the capital that night.

This man proved even harder to reach.

When he answered the phone, his voice was nervous and unsteady. He repeatedly insisted he was just a driver and knew nothing of Luka's activities. Multiple scheduled meetings were never kept, and eventually, he stopped replying.

We shifted our attention to Luka's possible escape routes, including neighboring Lebanon—where the Iran-backed group Hezbollah had close ties with the Assad regime.

A senior source in the Lebanese government told us he understood Luka had passed through Lebanon on a "good Russian passport but with a different name," before flying out to Russia.

We managed to find a man, now based in Lebanon, whose name was listed in Luka's contacts book, but under a number that no longer worked. He is one of many wanted by the new Syrian government due to his close association with the Assad regime.

This man, whom we cannot identify, said he had a number for Luka.

We saw it and realized it had a Russian country code.

Russia was a key backer of the Assad regime, and in the days after his fall, Assad released a statement confirming that he had fled there. Many of his inner circle were believed to have followed him.

Back in Luka's apartment in Damascus, we had found clues that Luka also had strong links to Moscow—awards from Russia's foreign spy service, and even a New Year's card addressed to him from a senior Russian official.

Now, the Russian telephone number for him suggested we finally had proof that he was—as we had predicted—in Russia.

We wanted to verify that this number truly belonged to Luka.

So a few days later, with us present, the man agreed to put the person he said was Hussam Luka on speakerphone and ask him questions which we believed only Luka would know the answer to, based on information gathered during our investigation.

The voice on the other end of the phone sounded confused but answered the questions instantly and correctly.

He refused, however, to speak to us directly.

But our contact later agreed to call Luka again and allow us to try to interview him.

The same voice answered, and we introduced ourselves, explaining that we had questions about serious allegations relating to massacres and torture committed by the former regime official.

"I can't take any risk talking on the phone in the position I'm in," Luka said, his tone anxious.

Asked if Russia was preventing him from talking, Luka said: "I cannot talk. I can't explain. You have to understand."

When asked if he would meet us outside Russia, he said: "It's difficult."

He then hung up the phone.

We later obtained a second number which we were told was also for Luka—this time registered in Syria and linked to social media and messaging apps which he appeared to be still using.

Over a period of a day, the BBC was able to locate him in two suburban areas on the outskirts of the Russian capital, Moscow.

The locations seemed far removed from the luxurious lifestyle Assad is reported to be leading in exile in Russia, and from the life Luka himself once led in Syria.

We knew we could not approach him in person in Russia, where Assad's henchmen are shielded from international journalists and police, so we decided to try putting our allegations to him over the phone once again.

We rang the number, and the same voice as before answered, the line crackly.

He asked who was calling, and when told it was the BBC, he immediately hung up.

We sent a message over WhatsApp, asking for his response to the many allegations against him, but he did not reply.

Confirmation that Luka is in Moscow is difficult news for those in Syria seeking justice. Russia is highly unlikely to extradite officials from the regime it long supported.

The Russian government did not respond to BBC requests for comment about Luka's presence there, or whether it would ever consider an extradition request.

Back in Homs, Mohammed says he will never abandon the hope that Luka, and other senior members of the Assad regime, will one day face justice.

"[I am] angry at all those who were with the regime and its security apparatus… They were all against us," he says.

"Wael was just a seven-year-old child… All he cared about was playing and having fun."

Additional reporting by Riam Dalati, Ghaith Solh and Abigail Akerman