Pandora 88, Purcell Room, London<br></br>Moving Africa, Barbican, London

On the scale of human phobias, the fear of being trapped in a small space ranks pretty high. Broom cupboards, lifts, even low-ceilinged toilet cubicles induce panic the minute the door won't open. As for being holed up indefinitely, it's hard to imagine. Which is partly why the story of Brian Keenan and John McCarthy's incarceration at the hands of Beirut terrorists in the late 1980s has taken so long to evolve as a film (Blind Flight is still awaiting a release date). Production companies were nervous of handling such a deeply unsettling subject. Two men in a box for four and a half years - can that be interesting to watch? A two-man show at the Purcell Room, Pandora 88, emphatically proves it can.

In a rare example of live dance-theatre getting ahead of the game, the 26th London International Mime Festival opened with a genre-defining offering from the German company Fabrik directly inspired by Keenan's memoirs. In Pandora 88 a box, barely 1.5 metres square, encapsulates the shared experiences of two young men (Wolfgang Hoffmann and Sven Till) who clearly would not choose such intimacy. Their steel-riveted prison is their living room, bedroom and exercise yard, their only source of light and sound, and a screen for memories of lives they struggle to remember.

Exploring the spatial limits of their prison in more ways than I'd thought possible, and helped by minimal dialogue, the pair reveal their changing states of mind with devastating clarity. Rage, despair, violence and listlessness, fits of crazy hope and hallucination jostle for precedence as they adjust to an existence whose physical pressures are all too real but whose psychological traps are unknowable.

Sleeping positions are a problem, and the tetchy duo find grim humour in their attempts to co-exist with comfort and decorum. By day (but what is day under constant electric light?) they play games to while away the hours, but "hours 'till what?" is the question that hovers dizzyingly over everything.

Likewise, director Andrew Dawson plays disorienting games with the spectator using spots of light to isolate the performers' body parts - disembodied hands move on the vertical like rain and faces float past like prizes on a carousel, madness made visual. Elsewhere he varies the pace to show the drag of endless time - the pair scaling the walls in boneless slo-mo - or its opposite effect in fast-forward robotics.

With bitter irony the men reminisce about the outdoor hide-and-seek they enjoyed as boys, devising ingenious ways of re-living their old freedoms - tapping the sound of retreating footsteps on the steel wall ("Coming, ready or not!"), or miming holding the nose under water. It could be coy. But the show so soundly secures our empathy with these two fragile souls that we snatch at the offer of humour with relief. Even funnier is a game of charades where one of them impersonates a shirt hung out to dry, the other exploding popcorn.

What might have been a grim dissertation on human frailty becomes, in these inspired hands, a glimpse into an extremity that thankfully none of us will ever experience, but which unlocks powerful truths about the mind and its resilience. That the innovative world of Pandora 88 also manages to include some traditional comic mime is the biggest joke of all. There is a tellingly self-conscious moment when one of the men catches himself feeling his way round the walls in the manner of a well-known beret-wearer. Then he gives it up as a lost cause, which it is, in the light of this.

By contrast, Moving Africa, a short season at the Barbican, promised to show how contemporary imagery and ideas are infiltrating African dance. Too bad that all three of the works shown by choreographers from South Africa, Madagascar and Burkina Faso - south, east and west - bore traits of the worst kind of European contemporary dance: over-long and wilfully obscure. Best was the offering from Salia ni Seydou, a piece amplified by the titanic physiques of its three male dancers and a bamboo-flute supremo who could laugh and blow at the same time. I swear much of the dance was intended as slapstick, but on Wednesday not a soul found it funny. Though I felt for the dancers, the reaction was reassuring. Too much globalisation makes art bland. Dance may be a universal language, but its regional accents must be kept.

jenny.gilbert@independent.co.uk