Theatre DEAD GUILTY Apollo Theatre, London
The attraction of murder stories is that an infinity of variations is possible in location, in motive, in method, but tied up inside a structure that is in essence beautifully pure and simple: you are given a cast of possible suspects, and one of them is the murderer.

Over the last century or so pretty well every variant on this structure has been tried out. The murder has come at the beginning of the story in a traditional whodunit, or been delayed to the end (when you hope it will be foiled) in a thriller. The murderer has been the most likely suspect, the least likely suspect or a suspect of intermediate probability from whom attention has been distracted - the vast majority of whodunits fall within one of these three categories. Out at the margins, there have been bolder experiments with the form - the murderer has turned out to be somebody who does not appear to be on the list of possibilities (the first-person narrator, the detective, a character who is already dead); or the victim has turned out to be somebody else entirely; or the murder has turned out not be be murder at all, but suicide or a freakish accident.

During Richard Harris's thriller Dead Guilty you find yourself toying with all these possibilities, because you can't believe that the identity of the murderer is as blindingly obvious as it seems to be (and I write as someone who has almost never guessed a murderer right).

For about 15 minutes at the beginning, while we're still being introduced to the characters, there is some lingering ambiguity: is Jenny Seagrove, laid up with a broken leg after the car accident in which her lover was killed, under threat from her yobbish, possessive odd-job man Gary (Niall Refoy), or from her lover's gentle, caring widow Margaret (Hayley Mills)? As a matter of courtesy, I can't give the answer; and if you can't guess from that description, there is a chance that you might enjoy the play.

Only a slim one, though. In terms of pure formal structure, it's perfectly well made, but within that structure very little of interest happens. Seagrove's character attempts some fairly half-hearted wisecracks, and there are a couple of moments of grim humour when Mills strays towards the truth about her husband's affair. Seagrove hobbles gamely, and Mills puts in some effective cushion-plumping to establish her fussy, middle- aged character. Otherwise, the main pleasures are speculative: will Seagrove's motherly counsellor (Angela Morant) turn out to be a serial killer? Will some completely new character turn up who isn't even in the cast list? Will Hayley Mills turn out to be a man? Will something, please, anything, even mildly unexpected, happen?

Nothing doing, though. The only question of any substance is, will Seagrove be saved? It's hard to care, though. One thing I think I can say without giving the game away is that the plot hinges on pain-killers and sleeping pills; and this certainly isn't a surprise in a play that's such a perfect anaesthetic.

n Continues to 28 October at the Apollo, Shaftesbury Avenue, London W1. Booking: 0171 494 5070