Nathan Cassidy has become one of the most popular stand-up comedians at the Buxton Fringe, coming here year after year and regularly getting rave reviews. But this year is a little different: alongside his stand-up show, he's also brought this new play. Watch This. Love Me. It's Deep appears an idyllic love story, but is it too good to be true?

The staging is very simple; Cassidy is alone with a pack of tarot cards, which he tosses to the floor from time to time, before bringing them into the story. He opens with an anecdote about him aged six, playing a trick on his mother in the swimming pool – only it’s not his mother, and it has all gone terribly wrong. Cut to ten years later, and he stands in the shallow end for two hours (the second most embarrassing thing you can do in a swimming pool), hoping to get to speak to the love of his life, the beautiful swimmer speeding up and down the fast lane.

As Cassidy explains, it’s only a ridiculous thing to do if it doesn’t pay off. It does pay off, and he goes on to expand on his perfect life with his perfect wife. He uses the cards of the tarot to make his points about how he has achieved this “all-embracing happiness forever”. He lays it on thick, to the point of irritation, but there are enough hints in his knowingness to warn us that a twist is coming. As he's said, it’s only weird if it doesn’t come off – so the question is, can he get away with it?

Structurally, the show is clever. There are the repeated references to certain touchstones: swimming, A Question of Sport, and the Tom Hanks movie Big – I loved the way the music from Big punctuates the performance. He goes a bit meta, starts addressing the nature of theatre and how it differs from stand-up, and dares the audience to heckle him. It feels like he is pushing his luck – but the show is about pushing things as far as you can, seeing what you can get away with, and how you have to do that to be happy.

There are some places where the material seems to wear a bit thin, and Cassidy dips back into conventional stand-up to pad things out. These sections are funny, of course, but they break the flow, temporarily lifting you out of the story.

So is this really theatre? And does it really matter? It's very different in style, but it reminded me of Stewart Lee in the way it takes the audience a long way up the garden path before bringing us back. As Cassidy ratchets up the tension, my notes are full of scribbled comments like “where is the catch?” and “how is he going to get away with it?” But he does get away with it, and getting away with it is a theme of the show. Not everyone will connect with such an audacious, high-risk strategy, but it is very clever and very good indeed.