The first 15 minutes of Wu Hsing-kuo’s one-man dance-opera of Kafka’s Metamorphosis are stunning. The remaining 120 minutes are, unfortunately, a masterclass in why scripting, directing and starring in your own production isn’t always a good idea. As the piece stretches on, on and interminably on – and also manages to inexplicably overrun by 40-odd minutes – it doesn’t develop or maintain the interest.

It’s such a shame because, as I say, the opening is brilliant. Accompanied by Wang I-yu’s atmospheric score and Ethan Wang’s absolutely breathtaking visuals and projections, we wait for something to happen – and it feels as though we’re waiting for something really special. Wang’s projections are like twisted rorshach tests, as monsters resolve into mountains and smoke flows upwards. A door opens in the set and we wait, breathless, to see what will emerge.

Wu portrays Gregor Samsa’s awakening with a gut-wrenching beauty and grotesquely apt movement style. Appearing from a dark doorway, Wu-the-man is almost invisible under Sara Lai’s incredible bug costume. Wu explores his new body with tender sincerity and trepidation, twitching his antenae and leaping around the stage as though trying to slough his skin. It’s an incredibly powerful, visual treat which also packs a serious emotional punch, as we watch Gregor’s horror develop. As he dances and writhes without speech, the music is enough and the potential for this to be something very special begins to swell. The first quarter of an hour is spectacular in the truest sense of the word.

Sadly, it’s all downhill from here. Wu’s Gregor starts to sing and this shatters the illusion of a speechless creature and the horror and fear are never recaptured. The adaptation is a truncated and strange one, drawing on six elongated scenes to tell the story of the man who wakes up one morning to find himself metamorphosed into a giant bug of some kind. The Mandarin script, which Wu also wrote, has been translated by Bi-qi Beatrice Lei, and it just doesn’t work in English. Lines with may well sound deeply poetic in Mandarin sound forced and odd in their English surtitles: his sister (also played by Wu) says at one point “My face and neck contend in beauty with the spring.” The high style doesn’t fit with the calm and matter-of-fact delivery.

If the show stayed with this style, though, it might start to lull its audience into its rhetoric and to engage us with this highly stylised form of words. However, it then starts to tell the story in a much more ordinary form of English, and this change of form jars with what has come before. And it’s all so, so slow. The score doesn’t develop or change much throughout, apart from a few small crescendoes – each time the music swells so does my hope that the piece is about to come to an end. Every sequence is far, far too long and become almost instantly repetitious. Couple this with the fact that the whole show feels as though it’s repeating elements of the first 15 minutes over and over again, and you end up with an over-long and leaden show that takes its sweet time to actually do anything.

Then there are the more baffling elements, such as a giant tuxedo-wearing figure who appears at Gregor’s death and pelts him with apples. I can’t pretend that I knew what was going on at this point. An extended scene where Wu plays his own sister, complete with skirt and blouse, feels entirely extraneous to the narrative (although it is beautiful to look at) and makes very little sense. For such a dark and meaty story, this version feels slight – it doesn’t really evoke Gregor’s isolation, frustration or fear and it just so drawn out and slow.

Perhaps I am missing the point in looking for meaning, for narrative, for any kind of drive, but this meandering production felt unbelieveably self-indulgent to me. There is no denying that Wu is an incredibly talented performer; he dances and sings superbly. But as a vehicle for showcasing his skills or conveying a story to an audience, this torturous show ultimately fails.

Metamorphosis is playing as part of the Edinburgh International Festival. For more information and tickets, see the Edinburgh International Festival website.