This is how ArtsEmerson describes their production:
... Combining breathtaking physicality and daring aerial action, the recently transformed Gregor lithely negotiates a gravity-defying split level set in this hugely acclaimed production directed and adapted by Gisli Örn Gardarsson and David Farr. With evocative original music composed by world-renowned musician and lyricist Nick Cave and long-time collaborator Warren Ellis from The Bad Seeds, the music emphasizes Kafka’s dream-like vision and turns it into an electrifying reality.
In short, the play itself being only about 80 minutes, it's about young Gregor Samsa. Samsa, as the audience has come to learn, has been the main (and only) provider for his household, which includes his supposedly ill mother; his father, who hasn't worked a day in the last five years but finds plenty of fault in his son's work ethic; and his beloved sister, Greta, whom Gregor encourages to pursue her love for the violin. Gregor, a traveling salesman, wakes up to find himself transformed into a giant bug, or "vermin," as his family comes to call him.
The key loss, however, is not that he's no longer a human, but that he cannot communicate with his family. This seemed to be the primary reason for his downfall; when Gregor speaks, the audience can understand him, but his family cannot. What the family actually hears is a hideous noise, which they cannot, obviously, understand as speech.
After the initial shock, which they never really get over, the family come to more-or-less accept that "their" Gregor is never coming back. His mother takes up sewing, his father returns to the workforce as a entry-level policeman, and Greta takes up a job at a department store. Much to the dismay of the audience (or reader), the family actually seems better off with Gregor as a bug. (Although Gregor remains horrified and feels terribly guilty, blaming himself that his poor family have to work.) It's like now that they can't depend on Gregor, they have to grow up, in a sort. This, to me, was the real metamorphosis in the story.
The story ends in a very Kafka manner; Gregor's demise comes about as a result of starvation (his once loving sister starts to ignore the fact that she has to feed him, saying, "Oh, I'll do it later" and then forgetting) and being beaten, by pretty much everyone, even Greta, who is so sweet and innocent at the start of the play. Once their son is discovered dead, the Samsa family quite literally goes out to celebrate. From their perspective, Gregor was this horrible monster that was bent on dragging them down with it, into the gutters of despair. (Although actually, what the Samsa family interprets as death threats, is Gregor trying to apologize for becoming a bug, which isn't his fault at all.)
Instead of dressing up as a bug (thank goodness), the actor was just dressed in a suit the whole time. (Until sometime in the second act, when his shirt is literally ripped of his back, that is.) And how on earth, I wondered, would they show Gregor as a bug crawling around the walls?
The set was incredibly clever: the second floor (the bottom being the kitchen/living area) was Gregor's bedroom, where he stays for nearly the entirety of the play, is done vertically. Imagine a bird's eye view kind of map, where it's like you're looking down from above and you can see the shapes of all the buildings and stuff. It was like that, except with a bedroom scene. And the way they did this was they made it so that what would be the floor of the bedroom was actually the wall facing the audience. Yes. The wall.
So everything was vertical- the bed, lamps, chairs, rug, table. And then they had Gregor climbing around on that wall in a way that it looked like he was standing upright on the floor, so he was actually holding himself horizontally for, again, pretty much the whole time. And all along the walls (and ceiling, if you want to be literal) were hand and footholds, like on a climbing wall. Then, when Gregor's supposed to be jumping around on the wall, they replaced a portion of the actual floor of the second story of the set with a trampoline, so he was literally bouncing on what was representing the wall.
Needless to say, it was a highly entertaining performance.