Sam Benstead’s piercing documentary charts what you might call an act of noble catfishing: how Amsterdam-based Syrian academic Annsar Shahoud adopted the online identity of “Anna” to coax an al-Assad regime stooge into admitting his crimes. It’s not clear if she and her collaborator, genocide studies professor Uğur Ümit Üngör, are part of the European vigilante networks that inspired last year’s fictional feature Ghost Trail. But the courageous, haunted and psychologically smudgy nature of this work is plain to see here.

When they first watch a video of what became known as the Tadamon massacre, Üngör and Shahoud are appalled at what they see: a procession of Damascan civilians casually murdered and dumped into a tyre-lined pit. They are also exhilarated to finally have incontrovertible proof of al-Assad’s brutality. By combing Facebook they manage to track down the Cheshire Cat-grinned head killer: an intelligence agent called Amjad Youssef. Posing as Anna, a Syrian expat writing a sympathetic thesis about the regime, Shahoud makes tentative first contact with Youssef by video call. For a spook, it is surprising how a few well-chosen signifiers work wonders on him: the portraits of Hafez and Bashar al-Assad on Anna’s wall, the Shia sword pendant around her neck.

Youssef has a very bad day in 2022 when the Guardian names him in a report. But while he is safe in what is then still regime-controlled Syria, the legal follow-through is uncertain. His eventual arrest in April this year is presumably what made the film’s release possible. Meanwhile, the ostensibly calm and focused Shahoud admits the deception is giving her psychological blowback; she describes Anna as a dissociative mechanism she uses to shield herself from the horrors of what she lived through in the early stages of the civil war.

Benstead outlines Shahoud’s quest with tight efficiency and, with a ceremonial send-off for her alter ego, is determined that she finds redemption. Closing the film to slightly pat effect, this is perhaps to the detriment of a greater understanding of the roots of violence in trauma and shame which, according to Shahoud, is a Syria-wide issue. In Youssef’s case, his rage and grief over losing his brother during the fighting seem to have in his mind justified his work for the regime. Yet we only get glimpses of his history, or of the other Ba’athist-side testimony collected by Anna. The thriller arc, compelling though it is, only takes us so far. It impedes the murkier and dramatically equivocal task of doing what very few films (like, say, Joshua Oppenheimer’s The Act of Killing) do: getting to grips with the perpetrators and the full corrupting spectrum of violence.