Keeping a chart of his neighbours' sex lives, compiled by way of a microphone planted in the party wall; donning an orange apron and pretending to work at B&Q; presenting his favourite supermarket cashier with a range of random, but complimentary, awards. These are just a few of the 'projects' that have kept Kim Noble occupied over the past few years, brought together and used as the framework for this extraordinary, unsettling, and very funny piece of theatre.

So involved are some of these exploits - most of which Noble also films himself undertaking - that it seems like he must dedicate his whole life to them. Various details of the real Noble - the man behind the obsessed artist, (not that it's necessarily even possible to separate the two) - are revealed now and again. He was taking antidepressants but he threw them away. He was with a wonderful woman but he's not anymore. You worry hugely about Noble, even as you're laughing in disbelief at the truly shocking things he gets up too (which I won't spoil for you here).

What could initially be mistaken for a rather messy series of almost boastful confessions is gradually revealed to be an intricately crafted interrogation of the human condition. Noble's dad, it turns out, is dying, demented and alone, and there's nothing his son can do about it. Constructing elaborate fantasy relationships with men he's met on Facebook in the guise of his female alter ego, and pushing the limits of those connections may not be how you or I would respond to such a situation, but it works for Noble (at least in the theatrical sense - beyond that, it's impossible to say).

Noble and co-director Gary Reich do not let the audience off lightly, lulling us again and again with silliness and fun before pulling the pin on a grenade of cruelty or smut. We're also actively involved in proceedings, broadening the theatrical scope of this one-person show. A woman is asked to put on a pair of headphones to listen to Noble's recordings of his shagging neighbours and then to follow the instructions she's given. She does little tasks around the stage, becoming a co-conspirator in Noble's game and helping to create the frankly magical grand finale of the performance. Another audience member is brought on stage to star opposite Noble, gradually transformed into a character in the drama as Noble makes his own elaborate transformation. It's compelling stuff.

Noble never shies away from presenting himself in embarrassing scenarios, but he doesn't have a problem humiliating his unwitting subjects in front of a paying audience either. He goes too far in this regard, but we let him get away with it. I don't quite know why. Perhaps it's because it feels like he's saying something that we need to hear.

Kim Noble - You're Not Alone runs at Soho Theatre until 9 January.