In summer, Scandinavians emerge from the dark into light, like moles coming to the surface, and this sense of idyllic respite, and intensified pleasure in the natural world, imbues Tove Jannson's 1972 Finnish children's classic, newly adapted by Jemma Kennedy for the Unicorn.

The 75-minute show, directed by Douglas Rintoul, is written in too many short and bitty scenes, some of them bordering on the inconsequential, but the atmosphere carries through, just about, and so does the glorious, strange, melancholic performance of Sara Kestelman as an ancient grandmother engaging in a series of snapshot philosophical discussions with her six year-old granddaughter Sophia (Sammy Foster at the performance I saw, alternating with Amy Snudden).

They inhabit a small holiday island in the Finnish archipelago, designed by Francesca Reidy as a stony, moss-covered promontory with bamboo canes supporting the flowers, and grandma's bed representing a sort of Prospero's cell; granny has no book apart from the one she's helping Sophia to write, but she has history, and wisdom, to impart, and she's furious with the vulgar usurpers in their holiday yachts.


"The poetry and descriptive beauty of the book hasn't been wrestled fully onto the stage"

There are worms and cow pats to be trodden on, a damp box of fireworks to celebrate midsummer, questions about the gender of angels (the mystery would be solved, Sophia suggests, by one flying under another's long skirt and looking upwards), memories of Venice and a salamander in the Grand Canal, sweet birdsong, lemonade and cognac.

The poetry and descriptive beauty of the book hasn't been wrestled fully onto the stage, but the coming together of the generations is well expressed, and you sense youngsters in the audience identifying strongly with Sophia's questions, her fleeting hints at domestic unhappiness (mother dead, father absent), her tentative sorties into a small canyon and the glistening waters around the rocks.

And Kestelman stalks her young charge with a benign, unsentimental indulgence, never talking down, while being pulled gently towards her own conclusion. There's a great moment when Sophia dives at last into the sea, followed by a trespassing adventure to one of the offensive holiday homes with its tin roof and barking dogs. And then the summer ends, the book is completed; granny takes once more to her bed...

The Summer Book continues at the Unicorn until 29 June 2014