"IT'S nine o' f***ing clock and it's time for some Beckett" a voice booms, then a fluorescent image of Irish playwright Samuel Beckett flashes up on the projector accompanied by thumping techno being played by a DJ in a vest who has suddenly appeared out of nowhere. Over the din comes an announcement that anyone who does not have a ticket for the Beckett DJ night must leave. After an extremely awkward 30 seconds where we politely wait to see the punchline, we realise that we really are being asked to leave and file out in a discombobulated shuffle, some crying with laughter, others looking more like they want their money back.

So ends Joseph Morpurgo's show Hammerhead.

I thought I would start at the end because that's exactly how Mr Morpurgo starts his hour-long, absurdist, PowerPoint-driven concept comedy show.

The concept is this: Morpurgo plays an actor/ director who has just staged a groundbreaking nine-hour, one-man production of Mary Shelley's Frankenstein. The show that we watch at the North Wall is an audience question and answer session afterwards.

The Q&A begins with a recap of the show, in which we are reminded how, over the past nine hours, we have just seen Morpurgo play all 937 characters in the story (including some we may not remember from the novel such as the comedy butler and 'the concept of wet'), then the man himself – still in his ragged Dr Frankenstein costume – comes bounding on stage to start taking questions.

The questions really do come from the audience, but they are scripted on cards which have been handed out to game-looking stooges beforehand. One can only assume this strategy sometimes falls flat on its face if the readers fluff their lines or, worse, go overboard in an attempt to join the fun. Tonight we don't go too far either way.

The final layer of conceit is that the audience's questions increasingly stray from script-writing and process to rumours about massive financial and critical failure and on to completely irrelevant subjects including a man who asks for advice on an office romance.

Interwoven with this is Morpurgo's PowerPoint show, which he uses to reveal some of most bizarre features of the play, including how Act 5 is actually an 'Easter egg' hidden inside Act 6, which he reveals by bringing up a slide of the script from Act 6 then zooming in thousands of times between two letters to reveal the whole of Act 5 written in microscopic type in a space smaller than a full stop.

As the almost hideously absurd details gradually reveal a mind on the brink, the stress of the audience's increasingly unwanted questions wear the director down until he has a breakdown on stage, demands the doors be locked and holds the entire audience hostage while threatening to cut his own throat with a promotional CD.

As a concept, the real show is almost as ambitious as the imagined one – it certainly requires the same buy-in from an audience willing to go on a journey deep into the unknown – but, on this night at least, Morpurgo's monster just about manages to walk the tight rope and avoid tumbling into the abyss.