First Night: The Curious Incident of the Dog in the Night-time, National Theatre

How to adapt novels for the stage? Following a fine old tradition of absorbing first person narrative into a third person drama, playwright Simon Stephens does for Mark Haddon’s brilliant cult novel what David Edgar once did for Nicholas Nickleby: and he makes it an ensemble piece about putting on a play.

In this case, it’s 15 year-old autistic genius Christopher Boone’s book that has been read by a sympathetic teacher and turned into a schoolroom drama; but with amazing lighting (by Paule Constable) that illustrates the mathematical equations and algebraic conundrums at the heart of Boone’s emotional crisis.

And Luke Treadaway’s remarkable performance in the lead is the best of its kind since David Threlfall’s as Smike in that same RSC Dickens extravaganza; less frenetic, but capturing that essential tone of headlong intellectual assurance and unguarded neediness.

Personally, I’m sorry the lad trades his rodent Toby for an audience-baiting real-live sweetheart puppy at the end. It’s a grisly sentimental moment at odds with the rest. But the rest is just terrific, starting with a great doggy corpse stuck with a garden fork that sets Christopher off on his detection trail. Who killed the dog? And then: where’s my mother?

Actually, the cutesy dog is prefigured in the toy trains that whizz round the theatre as the heroic journey from Swindon to Paddington begins. But the neat niceness of Marianne Elliott’s well regimented production is all part of the severe exactitude of Treadaway’s performance.

This is a profoundly moving play about adolescence, fractured families, mathematics, colours and lights. Having passed his exams, and poised on the brink, Treadaway returns after the curtain calls to explain how he answered the toughest A-level question: this is dazzling, especially for anyone like me who passed various maths O-levels (two, actually; elementary and additional!) without understanding a word of what I wrote down.

The show’s presented in a sunken light box, the actors carrying on like modern dancers – mixed feelings about this – choreographed by Frantic Assembly’s Scott Graham and Steve Hoggett, with wonderful acting cameos from Una Stubbs, no less, Howard Ward and Sophie Duval.

But this is Tread\way’s evening – as it should be; he deserves a lead role after marking time as Albert in Elliott’s co-production of War Horse – and he is superbly supported by Niamh Cusack as the teacher, Paul Ritter as his emotionally suppressed father and Nicola Walker as his estranged Cockney mother, first seen sun-bathing in a wonderful evocation of that long-ago family holiday.

To 26 October (020 7452 3000)