In December 2024 the world witnessed the dramatic fall of Syrian dictator Bashar al-Assad, ending a 13-year civil war. But behind the celebrations is a grim legacy, over 100,000 Syrians disappeared and more than a million imprisoned.

This week on Four Corners, a two-year investigation into one of the most brutal campaigns of state repression in modern history, as told by the victims and the perpetrators.

The BBC’s Surviving Syria’s Prisons gets rare access to more than 40 former regime operatives, from intelligence officers to the prison guards who oversaw torture and execution.

This chilling investigation exposes the mentality and motivation of those who tortured and the regime that enabled it.

Their confessions, told for the first time, are intertwined with the powerful story of two brothers who survived Syria’s most notorious prison Saydnaya, known as the “human slaughterhouse” to start a journey for justice.

The United Nations has said the torture and detention under the Assad regime constitutes crimes against humanity.

Surviving Syria’s Prisons, a BBC production, goes to air on Monday 29 September at 8.30pm on ABC TV and ABC iview.