In Marcelo Dos Santos’s new solo play, a comedian and “professional neurotic” peals away the surface of his wise-cracking veneer to expose a self-destructive but deeply vulnerable core. As the title, suggests, there is a growing sense that something terrible is going to happen, and may well have already happened, not least that the unnamed comedian might have to confront reality and stop distracting himself from his feelings and self-loathing with carefully crafted jokes.

In a bravura performance, Samuel Barnett brilliantly captures the style and engaging delivery of stand-up comedy, hand resting on a microphone stand as he shares his deeply personal story. Caught in a cycle of meaningless hook-ups, he finds himself going out with a handsome American – a relationship that feels too good to be true. But there is one problem: his boyfriend suffers from cataplexy, which means he can have a seizure or even die if he laughs – probably the worst-possible partner for someone who has chosen a comedy career.

With pinpoint-sharp direction by Matthew Xia, Barnett gives a mesmerising, flawless performance, lurching from hilarious to heart-breaking. But it is unclear how much, if any, of this professional comedian’s story is true. How much is he really sharing about his life, how much of it is constructed just for laughs? As his façade starts to crumble, he forgets to address the audience through the microphone, suggesting a rawer version of himself is emerging, unmediated by his comic routine, casting a disconcertingly ambiguous shadow over the show’s ending – and all that has come before.

The shifts in narrative are matched by Elliot Griggs’s lighting and skilfully supported by Max Pappenheim’s sound design. Genuinely funny with plenty of gags, the show explores the craft of stand-up comedy and its tenuous and shifting relationships to a performer’s real life as well as the challenges of finding connections on today’s gay dating scene. But most of all, it is a devastating, darkly comic study of a man trying to wrestle with the everyday pain and anxieties of his life.

Feeling Afraid as If Something Terrible Is Going to Happen runs at Paines Plough’s Roundabout at Summerhall at Edinburgh Fringe until 28 August 2022. Tickets at festival.summerhall.co.uk and edfringe.com.