There is, eminent young neurologist Alex tells us, no self. Our brains are simply a collection of cells and synapses whose interplay, rather than creating consciousness, is consciousness. His wife, meanwhile, is facing her own diminishing sense of identity as a brain tumour slowly saps her everyday abilities. And a freak accident with a futuristic device then poses yet more questions about how we define personal identity.

For a Fringe debut, York-based Mind Over Matter theatre company's beautifully delivered show is a bold achievement – not least because rather than shouting loud with every theatrical device imaginable, they dare to be calm, considered and reflective. Anna Mawn and Will Heyes' strikingly simple, elegant design, as well as Scott J Hurley's caressing music, give the show a gently futuristic, plastic feel that lodges long in the memory.

But it's On Ego's disarming mix of the cerebral and the emotional that marks it out as something truly special. At times, it feels like a thought experiment enacted on stage, and its central conceit is indeed pretty far-fetched – but the show is shot through with a tender, sincere sense of emotion from start to finish. All three of the cast deliver strong performances, most notably Oliver Henn as Alex in his opening TED-style lecture, which proves both enthralling and unsettling. It's a thoughtful, thought-provoking achievement.

ZOO, until 20 Aug, 2pm, £10 (£8).