We expect a Stoppard play to pull the rug out from under our feet. But his spy caper Hapgood, receiving its first big British revival since it opened in the West End in 1989, provokes such a flurry of rugs and feet that we never really know where we stand with it.

Tom Stoppard’s best work (Arcadia, The Real Thing, Rock’n’Roll) confers his cleverness upon us as if it were our own clear-sighted brilliance, merely mislaid until he reminds us where we’d put it.

Watching Hapgood, by contrast, feels like playing a horribly complicated board game and being the only one who doesn’t know all the rules. Can a story be simultaneously dazzling and dull? According to the science that underpins this Cold War tale, it can. Hapgood (Josie Lawrence) is a mother-hen British spy chief with a traitor in her ranks.

But the very notion of a single authentic identity is undermined by the quantum physics plied by her pet double agent Kerner (John Hodgkinson), who explains how an electron or a wave of light can be in two places at the same time. So, as Hapgood and her boys investigate treachery after a botched information swap in a swimming pool, the only reality is duality.

Hapgood is the supercool spychief, but also an embarrassing touchline mum watching her boy play rugby. Stoppard, who’s long depicted dual identities, absolutely crams this play with them – twin brothers, twin loyalties, twin particles, even twin Hapgoods. But it’s as emotional as a Sudoku session. Until a second act in which the heroine’s boy is kidnapped. Or is he?

Rachel Kavanaugh, the director, presents the clues lucidly and keeps up the pace. The minimal settings – a glimpse of a giraffe’s neck suggests Regent’s Park – are stylishly done. But a decent cast don’t always look as if they know what game they are playing any more than we do. Lawrence, in the part that was first played by Felicity Kendal, lacks the naturally patrician air that might make Hapgood’s playfulness credible. But she grows into the role in a second act that allows for more explicit play-acting (Hapgood impersonates her own sister – or does she?).

Mocking his own le Carré-like convolutions, taking us on an idiot’s guide to particle physics, Stoppard reminds us not to be too certain of our certainties. “We make bets on what makes best sense,” says Kerner in his Russian ehk-cent, suggesting that the assumptions that underline our simplest perceptions are bogus.

So maybe I’m mistaken in thinking that Hapgood is both half-baked and overcooked. Thematically, it’s a riot. Dramatically, it can’t quite contain its own brilliance.

To April 26. Box office: 0121-236 4455. Then May 1-24, West Yorkshire Playhouse

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