The Valley of Astonishment, Young Vic

“If we go to the theatre, it’s because we want to be surprised, even amazed.” Peter Brook’s programme note for The Valley of Astonishment stresses emotion and sensation above all things. How curious then that the play itself should be so cold, so cerebral a thing.

In unpacking the mysterious valley of the human mind, Brook has become so engrossed in his subject matter and its scientific facts and phenomena that he forgets to add the drama that they need to move from lecture to theatre.

Brook’s latest work – another collaboration with writer and director Marie-Hélène Estienne following The Suit – explores synaesthesia, the condition in which senses become confused, and sufferers’ sight, smell, touch and hearing become muddled and connected. We explore different variants and presentations of the condition in a series of human case studies, each clustered satellite-like around the central story of Sammy Costas (Kathryn Hunter) – not a woman, but a “phenomenon” who can remember anything.

Structurally there are some odd imbalances in the work

A cast of three actors (Hunter, Marcello Magni and Jared McNeill) and two musicians (Raphael Chambouvet and Toshi Tsuchitori) feels overloaded, crowding the delicate vignettes and simple set with bustle and role-shifting. But under all these goings-on, it feels like there’s a great one-woman Kathryn Hunter vehicle trying to emerge. Characteristically warm and wry, bright and wise, Hunter brings all the humanity and the emotion so lacking elsewhere, compelling even as she recites lists of numbers or nonsense syllables.

Perhaps Brook himself felt the lack, the hollowness at the centre of the show, because he frequently supplements the dramatic action with live music. Apart from adding another sensory dimension, the sole role of these musical interludes and commentaries seems to be to shape emotion and reaction. It feels like mood music in the crudest sense, a crutch for drama that isn’t doing its job properly.

Structurally there are also some odd imbalances in the work. The primary focus throughout the evening is on Sammy – her experiences, her development, her career. But suddenly in the latter half of the play another fellow variety show novelty act (played by Marcello Magni, pictured right with Jared McNeill) steps forward for a long sequence of card tricks involving audience participation. The episode is far too protracted (perhaps our audience was unusually reluctant), adds little to the theme already tidily summarised – “it’s too easy to reduce a human being to details” – and risks unbalancing the narrative for very little dramatic gain. The stories are also interspersed with extracts from the traditional Persian epic The Conference of the Birds – another connection that is never quite made.

There are moments of pathos and interest, beauty and Brook’s usual directorial control, but these don’t quite fill the gap where the play’s heart should be. The Valley of Astonishment is a work that wants to tell you so much that it forgets it could just show you instead – less theatre of astonishment than of interest mildly piqued. The topic is a fascinating and a tough one, but I couldn’t help wondering what a company like Complicite might have made of the same material.

• The Valley of Astonishment is at the Young Vic until 12 July 2014