Focus on Forsythe, Sadler's Wells, London

Tracing the steps of life and death

The Sadler's Wells celebration of the choreographer William Forsythe ends with a month-long bonanza, going beyond dance works and beyond the theatre itself. Over the next month, Forsythe installations will be set up around London, from nightclubs to galleries to a railway goods shed.

Forsythe, an American based in Germany, is probably best known for his wrenching, aggressively fast ballets. These earlier works are in the repertory of most major companies worldwide. With his own company, Forsythe tends to make works with speech, with more explicit use of theory, with deconstruction. There's an obvious overlap with conceptual art, something this Sadler's Wells season makes clear.

The performance installation You Made Me a Monster is in this category, putting the audience on stage with sculpture and dancers. When the show begins, it's dance as geography field trip, with the audience parcelled into groups, taken to on-stage tables and given tasks. The tables, about a dozen of them, have long metal rods, with cardboard shapes wound around them. The cardboard comes from models of skeletons, though they've been built up at random. We are urged to keep building, adding more cardboard bits to the growing sculptures. After that, we make pencil tracings of the shadows cast by the tangled, skeletal bits. The tracings make a script for the dancers, so the performance changes every time.

The other script is projected, line by line, onto a screen. It's an account – without names, just "my wife" and "I" – of Forsythe's wife's death from cancer. It focuses on details: how he and his wife felt treated by doctors, how they were creating a piece on xenophobia, with images of the body invaded from within. He remembers her as a dancer, how illness affected her body, her smell. The cardboard skeletons are another memory, a Christmas present. Years after her death, he made up the skeleton, but at random, not according to instructions. He created "a model of something I understood. It was a model of grief."

Then dancers start to move among the tables. Their movements look uncontrolled. Heads twitch spasmodically, feet are twisted on to their sides, hands curled up into claws. They howl and mumble as they move. Bursts of electronic sound build and clash.

The dancing is in sync with the projected lines of script; the one female dancer twists and roars as the text describes the wife as a dancer. The screen also shows images of hands building the skeleton. As the script reaches Forsythe's image of "a model of grief", I noticed for the first time that the hand wore a wedding ring.

That lucid prose is the strongest thing in You Made Me a Monster. Forsythe's memories are both clear and angry, evoking rage and grief. The audience's skeleton-building exercise makes you focus on the narrative. How much does the dancing really add? The lurching and howling express inarticulate grief, but are less powerful than the personal experience of the text.

There are more installations around the theatre. In the film Solo, you can see Forsythe moving from classical ballet into his own twisting, wrenching vocabulary. Here, the twists get repetitive, frantic for too long. In Suspense, Forsythe ties himself up in ropes, sometimes dangling for a while before screaming and untying himself.

The strongest film is the double video Antipodes I/II. Set up opposite each other, two films show Forsythe dancing around a table. One is hung upside down: the other side of the globe. In both cases, up isn't where you think it is. In the right-way-up film, what looks like a wall (with a poster and a first aid box hanging on it) is a polished floor. Forsythe plays games with space and perception, a slide becoming a jump.

City of Abstracts, set up in the foyer, is the most fun. This installation films people as they pass, projecting but also distorting the image. There's a time delay, so your movements don't show up immediately. Sometimes wild ripples go through the image, a single body suddenly undulating or being pulled into loops around other figures. The weird, shimmering image makes you look at how people stand and move, then breaks it into a whirling abstraction.

Focus on Forsythe season continues until 10 May. Box office 0844 412 4300