Without a doubt, one of the most haunting short documentaries to have crossed my path in recent years is The Last Days of Peter Bergmann. Invoking the voyeur in all of us, the film tracks a captivatingly incomplete picture of the last four days in the life of a man intent on disappearing into thin air.

Documentary-maker Ciaran Cassidy came across the incident when it came up in the Coroner’s Court, but knew the story would be fairly raw. He left it for a year, waiting until it became a cold case, then contacted the guard who was involved in the investigation – who remarked that it was one of the most affecting cases he had worked on after thirty years in the force. “I knew then that it wasn’t just me. People who had been involved in the case wondered about who this guy was and what his back story was.”

The documentary relies significantly on CCTV footage, of which there was thirty-two hours to trawl through. Interestingly, the purple bag he is constantly carrying makes him immediately identifiable, even to cinema audiences on grainy CCTV images, there was no need even for a close-up.

For me the most striking part of the documentary is the warm spotlight it casts on the community of Sligo and their responses to their fleeting personal interactions with the man. The anecdotes are poetic, heartfelt and remarkably lyrical. One woman interviewed in the film went home and wrote a short story on the man after she saw him, before she became aware of the circumstances of the man’s presence on the beach. “Whatever he was doing, he was leaving this far bigger imprint than he could have imagined. In his own way, he affected people and people responded to him.” For this reason, Cassidy found his subjects very willing to speak on camera “I think there’s a genuine feeling there that they want him to find his family and return home, because whatever he was planning didn’t really work out.”

Over the past couple of years, the film has had an impressive festival run (Sheffield International Doc Fest, Sundance Film Festival and Cork Film Festival to name a few) and sparked a great deal of debate – just take a look at the comments on Reddit for a start. As the jury who awarded Cassidy the “Best Documentary Short Film” award at the Melbourne International Film Festival noted – what really makes this film special is the way in which Cassidy “manages to invert the mystery genre from whodunnit to why” and “leaves the audience rooted to their seats as they act out the role of both spy and detective”. Jack Quilligan’s music helps emphasize the haunting nature of this strange little film –but Cassidy has no judgement. There’s no allegory, no contention, just the unexplainable.