Theatre The Invisible Woman The Phoenician Women The Gate / RSC The Pit, London

On the London stage now are two deeply divergent approaches to classic texts. At the Gate: a Roman comedy in a free, updated adaptation which arranges a calculatedly queasy clash between values then and now. At the Pit: a Greek tragedy in a production of such purist rigour and cultural empathy that you are handed a sprig of thyme rather than a programme on the way in. Programmes, as potential distractions, are banned until the end.

Paul Godfrey's The Invisible Woman is a reworking of Terence's The Mother- in-Law. Running the full length of the Gate's interior, Lucy Weller's set almost makes you laugh out loud. As a modern substitute for the row of front doors that's often the location of Roman comedy, a hotel corridor confronts you, more than faintly absurdist in its looming proportions and single shade of tomato soup. This is the world of key-cards and of piped muzak which washes over the proceedings with implacable empty-headedness throughout.

What happens in this confined space soon wipes the smile off your face, however. Terence's play depends upon an indulgent attitude towards rape that a contemporary audience cannot but find repugnant. A young wife has gone into hiding to give birth to the baby that is the consequence of an assault she suffered before her marriage and which she has kept hidden from her husband. The husband's former whore and the recognition of a ring bring it to light that the rapist was none other than the husband.

In Terence, with a certain amount of covering up, this produces a happy ending. In the current drolly sour version, directed by the author and Ramin Gray, what it leaves is a very nasty taste. The whore is degradingly and cheaply bought off: "Is this justice or just this?" she asks, with a saddened shrug at the shabby small-spiritedness of the episode. The effect of the updating is to make The Invisible Woman feel like a watered- down problem comedy, an All's Well That Ends Well without the heart.

It's not muzak but ritual chanting that vibrates through Katie Mitchell's stunning account of Euripides's The Phoenician Women, transferred to the Pit from Stratford. Like Henry VI Part III, which she recently staged, this play is about civil war, centring on the fratricidal strife between Eteocles and Polyneices, the sons born from the incest of Oedipus and Jocasta. Once again, though, Mitchell leaves the modern Balkan parallels implicit in a production which, with its candlelit statues of the gods and its formal intensity, makes the extremities of suffering feel at once immediate and immoral.

The principals emerge from and blend back into the mixed-sex chorus who, in their long rust and brown-grey coats, swirl and stamp around the stage, beating rhythms on breasts and floor, reacting to the horror as innocent in-transit foreigners trapped there by the invasion. The passion, the control and the slow suspenseful pacing of the action call for the highest praise. As Antigone, Lucy Whybrow makes a shattering transition from a nervy, excited girl to an adult whom grief has left ecstatic with principled outrage. You hear, abstractly, the massing of flies when the dead bodies are dragged in - just one of many fine details in an unbroken, punishingly powerful two-and-a-quarter hours.

n The Gate: 0171-229 5387

The Pit: 0171-638 8891