It's a staple concept for a Fringe parody. A group of self-important thespians stage a Very Important Play – which promptly descends into comedic farce, as their all-too-evident shortcomings are revealed. In this new show, comic duo Willis and Vere run with this basic idea as far as they can possibly carry it, aiming to subvert the most serious story imaginable with the most farcical events they can.

The "serious" story they're putting on is the "real-life" tale of a Holocaust survivor, which our hapless duo tackle in a predictably offensive style. The joke here is very much at Willis and Vere's expense, and the ham-fistedness of their approach is absolutely the point of the humour. But at the end of the day, there are scenes set in Auschwitz, and we're supposed to laugh at them. The ludicrous finale to this opening segment is heightened enough to get away with; the rest of it, I thought, struggled to justify itself.

But this is actually only a very small component of the total show. Before long, there's an incident – an incident which leaves at least one dead body on the stage – and the "serious play" is abandoned, as an increasingly convoluted cover-up ensues. This isn't, it turns out, really a two-man show. More actors appear from unexpected directions, and the grotesque humour turns more towards a slasher-flick than Schindler's List.

The elements of farce are there: the situation gets increasingly ridiculous, characters come and go, there are absurd leaps of logic and someone ends up with a gun Superglued to his hand. But on the day I attended, it lacked the fluidity and crispness that this style of performance demands. There were isolated moments of high farce which provoked a genuine belly-laugh, but they didn't link together or build on each other. There was simply too much dead time in between.

But they get the benefit of the doubt, and that third star, because I recognise that the circumstances of this performance were far from ideal. On a hot day, the Warren's shipping-container "Blockhouse" venue turns into an oversized roasting-tin; I honestly can't remember being so uncomfortable in a theatre, and I was only in the audience, not attempting to deliver a high-energy farce on stage. On a better day – and in a more suitable space – I can see that the comedy might ignite in a way it just didn't this time.

A Serious Play needs some serious work, I think, if it's to match Willis and Vere's previous success. But the idea behind it isn't a bad one; with more content and a higher tempo, it might yet grow into the outrageous comedy it hopes to be.