On The Line is the directorial debut of Oliver Pearn.  It's a 1960s-set thriller where we follow lonely switchboard operator Agnes (Victoria Lucie) who spends her days connecting calls and passing time by eavesdropping on conversations. However, one call proves unsettling for Agnes, drawing her into the kidnapping of dementia suffer Shirley (Dame Harriet Walter). But the crime isn’t as simple as Agnes thinks, and she soon finds herself drawn ever deeper into the investigation.

The first thing you notice about On The Line is the initial strength of the format; a single character in a locked room. Pearn creates a great sense of detachment in the first moments of the film with Agnes trapped in her own world where she only experiences human contact in a very artificial way, the claustrophobic location is perfect for setting up this loneliness. However, the novelty can’t be sustained for the whole film, and once Agnes starts getting more involved with the crime and more characters are introduced you wind up thinking ‘why isn’t this a radio play?’ The nature of the medium of film is that you can show rather than tell, but On the Line is formatted entirely around telling. It’s the same issue I had with the Tom Hardy film Locke, which was also a single-location story told mostly through phone calls. It feels like a story wholly unsuited to film, but the Inside No.9 episode Cold Comfort proves you can tell a compelling mystery with the single room/phone call concept.

It helps that the central mystery of Pearn’s film is genuinely compelling. Plenty of twists and turns that I won’t spoil but I do think that the central twist was telegraphed too much resulting in its reveal being a bit more mundane than the filmmakers would hope. But the writing is a clear strength, especially when it comes to Agnes’ characterisation,. She’s written as this very distant soul who finds her way back to appreciating human connection throughout the film, despite the horrific circumstances which kicked that off. The one scene that I think endears you most to Anges is early on when the sound design uses overlapping voices to respond to Agnes’ operator script, it creates that loneliness which is integral to the film's make-up. Victoria Lucie (Napoleon, Lord of the Rings: Rings of Power) brings a quiet dignity to the character with a very subdued performance which gradually slips into something more animated and alert.

On The Line does set out a promising career trajectory for Oliver Pearn, especially with his focus on characterisation and depth of personality. However the film suffers from the limits of the story’s format, it just isn’t a very filmic story and would have been much better suited to the radio or theatre where the intimacy of the location would have been more effective. A good central mystery and performance stops the movie from feeling like a slog, but you can watch this with your eyes closed and equally enjoy the narrative.