Sticky-back ectoplastic; FRINGE ROUND-UP

The logo of Improbable Theatre pictures a fish in a suit and tie struck by lightning while it sits on a chair, beside which the strange story of 70 Hill Lane (BAC) appears the essence of normality.

When he was 15 years old, Phelim McDermott's home was visited by a poltergeist. The ghost came without warning during one half-term holiday. Emanating from a disused playroom in the attic, it hurled small objects such as ping-pong balls and teaspoons from just beyond McDermott's peripheral vision, played grandmother's footsteps and, in his friend Karl's house next door, tore the light fittings out of the ceiling. With an affection the errant spirit scarcely deserved, the two boys nicknamed it "Polty". His stay was brief. After three days, Polty departed as unexpectedly as he had arrived. But he gets the most brilliant of valedictions, a funny, moving and dazzlingly inventive mixture of visual theatre, puppetry and good old-fashioned storytelling. It consolidates McDermott's growing reputation as one of Britain's brightest theatrical innovators.

Someone recently described 70 Hill Lane as "Blue Peter meets Blue Velvet", a reference to the way it plunders the kitchen drawer and the stationery cupboard. A sheet of old newspaper becomes an old woman lying on her deathbed begging a nurse for a cup of tea. The claustrophobia of a nightmare is evoked by pulling sticky-back plastic over McDermott until he's wrapped in a horror-film alien cocoon. Above all, though, there's Sellotape, with which McDermott and his fellow actor-puppeteers Guy Dartnell and Steve Tiplady draw 70 Hill Lane, like a 3-D architects' plan, switching from one view (the exterior of the house, say) to another (Polty's lair) so quickly that the effect is almost cinematic. When Polty himself finally appears he is a Sellotape homunculus, shining like molten gold under the lights.

It sells 70 Hill Lane short, however, to dwell too much on its technical accomplishments. McDermott's achievement is that he has taken a dinner- party anecdote and broadened it out into a story that touches upon (among other things) the loneliness of living in the big city, the way families relate to each other and the divided self. If you don't notice it at first, that's probably because McDermott doesn't look like a serious figure (imagine Nigel from EastEnders after liposuction to his cheeks). He has a stand- up comic's rapport with an audience, and a deceptively throwaway delivery that comes from years spent improvising. By the end, however, he has managed to convey something with far greater depth than your average tale of the unexpected. As McDermott himself puts it: "Doing the show now, I wonder if I am going back to myself then and haunting myself."

Sellotape seems to have played its part in Beatrice on the Frankfurt Express (BAC), too, as if the Glee Club's new show had been sticky-taped together from lots of little bits. Of course, that's how it's meant to look: ragged and provisional, artfully artless.

The cast come on stage and tell the audience as much at the beginning. No, they've never been to Frankfurt. And they don't know anyone called Beatrice. And they're a bit nervous. And they'll probably cock it all up at some point. And watch out for one of the performers blushing: it happens every time they do a show, and it's not always the same person. It's going to be messy, they seem to be saying, but then what do you expect, isn't that life? And besides this is a show about "waking up one morning to find that you have pissed on your bonfire and your bladder is far from empty".

The nearest thing to a structure is a surreal train-ride, interrupted by scenes in which, for example, one of the cast rambles on about what she feels like upon reaching 30 ("Scene 5: Ursula talks crap") or the whole company sings a silly lullaby in a made-up language.

Taken bit by bit, it seems both puzzling and inconsequential, though not without a certain slacker charm. But, as the journey progresses, I found myself slowly won over by the gentle melancholy of this sketch-show without punchlines, a journey peopled by lovelorn passengers and cartoonishly doleful train-drivers (seen only in silhouette) who edge towards making declarations of love as they share a lunchtime cheese sandwich.

`Beatrice on the Frankfurt Express' is at Battersea Arts Centre, London SW11 (0171-223 2223) to 9 Feb. `70 Hill Lane' and Improbable Theatre's improvised show, `Animo', are at the same venue from 11-23 Feb