You'd be forgiven for thinking Australian Olympic swimmers of the 1930s might hold little interest among the festival's bolder, brasher offerings. But don't discount this quietly powerful solo show from writer/performer Alice Mary Cooper. She leads us through a tender account of the life of Elizabeth Moncello, who died in an Edinburgh hospice earlier this year at the age of 95. And who learnt to swim following a childhood tragedy by copying fish, penguins and dolphins, off the shore of her island home Down Under, and invented the butterfly stroke that judges reluctantly accepted at the 1936 Berlin Olympics.

But far from being a hard-edged celebration of elite sporting achievement, Cooper's inspirational show is more of a calm reflection on the quiet virtues of perseverance and single-minded determination, on moving untold stories and inner resilience. Its origins as a children's show – it featured in Edinburgh's Imaginate festival earlier this year – are sometimes evident: why no mention of the dark Nazi backdrop to the 1936 games, for example? But Cooper's careful, considered storytelling and the show's emotional directness make its punch all the more powerful, and its message of dedication and self-belief, never overstated, is relevant to audiences of all ages. A modest gem of a show.

Summerhall, until 28 Aug (not 15, 22), 10.10am, £9 (£7.50).