When you've got a show as accessible and successful as this co-production between the Lyric Hammersmith and Icelandic company Vesturport, it's worth under-going metamorphoses with the cast if there is still an audience eager to fill another run. Thus the brainchild of adaptors/directors David Farr and Gísli Orn Gardarsson plays in W6 for the third time but without the acclaimed Gardarsson in Kafka's central role of man-turned-insect.

Intriguingly, no one here actually specifies what travelling salesman Gregor (Björn Thors) awakes to find himself transformed into one seemingly mundane weekday morning. Nor does he, but the horrified screams of his family make it clear that he has become one of society's untouchables, to be locked away, forgotten about and ideally starved to death. "Solving" his problem is the one response that is never going to get a look-in.

The niftiest idea comes in Börkur Jónsson's split-level design of the Samsa family's house. Downstairs is the conformity of the dining room but directly above a startling thing has happened: Gregor's bedroom has been rotated through 90 degrees. Thus the bed is now flush with the wall and the lamp stand sticks out like an exercise bar. What else is Thors to do but swing on it?

Thors's agility is astonishing; his feet don't seem to touch the ground as he leaps about, clings to the ceiling and tries to see his family by sliding headfirst down the banisters. We could do with more of this athleticism during the stolid central section, when the family attempts to take in a lodger and the whole piece threatens to become a simple satire of bourgeois values.

This 1912 novella is, of course, an allegory that can be pulled in all sorts of directions but Farr and Gardarsson somewhat limit its potential by relocating it to the Thirties and flagging up ominous indications of the rise of Nazism.

By the end, Unnur Osp Stefánsdóttir's impressively feisty Grete seems a prime candidate for the Hitler Youth. Overall, though, it's an enjoyable nightmare of an evening.

• Until 2 Feb (08700 500 511, www.lyric.co.uk).