Earlier this year, Jon Haynes, co-artistic director of Ridiculusmus, listed on his blog several things that “may have contributed” to the company’s new show. One was reading a book by the psychiatrist RD Laing as an undergraduate and “finding the idea of madness quite attractive”; another, being sectioned and discovering that “madness wasn’t so attractive after all”. The four characters in The Eradication of Schizophrenia in Western Lapland are all experiencing or assimilating mental illness in ways that are funny, fragile, unsettling and touching to witness. Madness looks confusing, painful, exhausting. It also looks a lot like ordinary life.

That’s down to the ingenuity of the staging: the audience are divided on either side of two rooms connected by net-curtained windows. In one, a mother is exhibiting signs of psychosis, to the bemusement of her sons; in the other, the eldest son is talking to his psychologist from his own state of psychosis, possibly triggered by his parents’ divorce. Sound bleeds from one room to the other, blurring the stories. Even when the audience swaps sides and the action replays, it’s a struggle to put the pieces together. If the eldest son – played with deadpan concision by Haynes – is “mad” in one room and “sane” in the other, what’s the difference? Is his psychologist – a deliciously distracted performance by the other half of Ridiculusmus, David Woods – also hearing voices? There’s something electrifying yet oddly reassuring about this experience: what does it matter if nothing makes sense?

Embedded here is an argument for a different treatment for mental illness, practised in Finland, that embraces dialogue with a community, not just a patient. There’s room for the show to develop, but already it’s a startling piece of work that challenges how you listen and fathom what you hear.

The latest transmission from Ridiculusmus is in, and it’s as dense and audacious as it is vital. A family drama and a meditation on schizophrenia collapsing simultaneously in on one another. There is no roadmap to guide the audience through their experience of the play, and no sense that the company’s process of development has culminated – instead there is trying and failing, trying and succeeding, trying and succeeding in being rather trying, and everywhere dialogue, contradiction and contemplation.

The audience is divided in two, and positioned at either side of a partition. One side presents the interior of a house, and behind its curtained windows the other side is a psychiatric ward. Two sections of the play run concurrently, with characters stepping in and out of their scene and into the other, and dialogue synching into parallel or reflecting at strange angles like theatre overhearing itself.

Its surface is smartly suggestive of psychotic experience: we hear voices we half-recognise but can’t understand; we suspect something is going on without our knowledge or consent; our sense of existing within a coherent community is disrupted; time slips, slides and folds in on itself. After the interval, when the audience switches sides and the play appears to begin again, it obtusely refuses to, as if gaps have unnervingly opened in our memories.

The family drama is extremely funny and often heartbreaking, the pressures that mental illness can exert across multiple generations are rendered with those touches of ‘serious laughter’ which Ridiculusmus have made their calling card. Patrizia Paolini is notably brilliant as Mum, whose own schizophrenia is doomed to recur in her son Richard. Conversations which toss discussions of food preferences in with threats of violent machete-murder are absurd but harrowingly real. Imagery becomes increasingly obtuse, until the final act in which the family becomes sort of Jungian archetypes or visitors from Richard’s psychosis. Bulls, Adolf Hitler, chintzy toilet roll holders – chunks of a mind cast adrift that wash back in in newly threatening dimensions.

Behind all this, Haynes and Woods are staging a number of discussions. There’s a plea for wider understanding of illnesses such as schizophrenia, of the vicious capitalism of drug cartels which suppress so-called ‘talking’ therapies in favour of pushing their medication, of the power of dialogue to pry open and to heal.

There’s also a brilliantly staged discussion of what theatre is, and what it means to be an audience member. When the Doctor character quotes R D Laing’s Politics of Experience, ‘Your experience of me is not inside you./My experience of you is invisible to you./I cannot experience your experience./You cannot experience my experience’, within the context of this fragmented, asymmetrical production, it’s a reminder that all experiences of theatre are essentially monadal and mediated by the infinitely centred nature of experience itself. It puts schizophrenia on context, it reminds us that in many ways schizophrenics have simply stepped ‘out of line’ or failed in their attempt to ‘play along’ with this prescribed pantomime of a communal perspective, but it’s also a forceful statement about the act of watching and interpreting theatre.

The Eradication of Schizophrenia in Western Lapland is intelligent, formally liberated and bloody peculiar. It’s doubtlessly still evolving, and could perhaps shed a little of its obscurity, but as both seriously thought-provoking and seriously funny theatre, it sees Ridiculusmus (remaining) at the very top of their game.

If the title is a mouthful, the show itself is a mindful. Commissioned by SICK! Festival Brighton, The Eradication of Schizophrenia in Western Lapland somewhat playfully engages with the rather weighty topic of schizophrenia, namely a treatment known as ‘Open Dialogue’, which has practically achieved the effect proclaimed in the title. The list of thanks in the programme is testament enough to the amount of research behind it, though this research is sensed rather than seen or heard in the show itself, to its great advantage. The research and subject matter led the creators, Jon Haynes and David Woods, to try to embody the illness and its unconventional treatment within the play itself, by experimenting with its form, content and delivery. They play with multiple or uncertain meanings, voices and audience experience to create a powerful and sometimes unsettling picture of mental illness.

The first commendable point is the mechanism by which the audience is split into two halves. So often heavy-handed and intimidating, here we are simply handed a coloured sticker, which determines which side of the council chamber we are to sit on. In the centre is a wall dividing the action and the audience, but allowing certain movements and interactions between the two. With this clever but simple design by George Tomlinson, the company hope to achieve “a simultaneous performance of two plays”. It’s debatable whether what is experienced by one half of the audience constitutes an entire play, but what happens in the interplay between the two is far more interesting.

In quieter moments, one could hear and partly see what was happening on the other side. Performers would speak through the wall, inexplicably pass through momentarily and then return. I became fascinated with the divergent experience that the other half of the audience were having, and the sneaky suspicion that they might be having a better time than me. This is a not only a lovely metaphor for the ‘grass is always greener’ phenomenon; the feeling that there is meaning and a fuller reality just out of reach also seems an elegant illustration of what moments of living with schizophrenia might be like.

Although characters often act inexplicably and bizarrely, this is never overdone, and always seems as if it follows some kind of internal logic, unknown to us. All performances are subtle yet powerful, particular that of the only female member of the cast, Patrizia Paolini. Characters seem to occupy an unstable position – sometimes being sane, sometimes not; sometimes being children, sometimes not; and sometimes being alive, and sometimes being dead – or never alive at all. The multiple narratives of the play never quite emerge into a cohesive or coherent whole, which though unsatisfying, is of course completely appropriate for the subject matter. The tone of the piece is distinctly negative and unsettling, which might seem strange in a piece about an almost miraculous, hopeful method of treatment for schizophrenia. The truth is that this cure, like so much of the play, though now in sight, remains just out of reach.

If you like your hand held when going to the theatre, this show is not for you. The Eradication of Schizophrenia in Western Lapland is a stimulating, confusing unfolding of events where the audience hear two performances at the same time and swap seats half way through. The aim is to introduce people to the experience of schizophrenia.

This is a clever approach. It allows you to empathise with people who experience the world in such a radically different way it can be hard to find anything to relate to. It is an open door to understanding, which is the first step to removing the stigma around the condition. This is Ridiculusmus’ stated aim, and they are very successful.

It isn’t always a fun experience, but then it never claims to be. It is highly confusing, but then I feel that this is the point. Four superb actors interact over a set you can see and one you can’t. There are multiple times, places, characters all of which achieve synergy and slip into disparity. It follows the story of a mother and son, both of which I assume have the condition (it is never mentioned) and opens a portal into their life, their relationships and a dire turn of events.

The set is as nimble as the dialogue. It allows a split audience to see certain things but not others, it masks and reveals in a tantalising fashion. The DIY-look costumes assist this and the weirder they get, the more disturbance they manage to imbue.

There are some marvellously funny sections, mostly led by Patrizia Paolini, and many downright disturbing ones, all blended together. We humans like narrative and consistency and this performance breaks many theatrical conventions to achieve a wormhole through which anyone can pass. An example of this is one actor playing two characters, yet barely changing anything to differentiate between to two – one minute he’s saying he’s twelve, the next he’s asking his son to obey his mother. Reality is broken apart.

Whilst this play is very successful in achieving its aim, it fails to signpost to give sufficient context to the confusion. No one ensured I picked up the program (I nearly didn’t) and here only is the landscape and ambition of the work explained. Luckily the venue was bright enough for me to read it easily during the performance – and I needed to several times. If I hadn’t reread my program I wonder if I would have walked out with a jumble of erroneous ideas from a jumble of senseless actions. There is power in this – but it negates the stated aim of the play.

I can see how giving too much context within the body of the play may ruin the adept writing and absurdist naturalism, but a short verbal explanation at the start or the insistence people receive and pay attention to the program would have sufficed without destroying the spirit.

The Eradication of Schizophrenia in Western Lapland is well worth seeing, but do treat it like a performed academic paper with the program as the abstract.