There is a mad person on stage, and plenty more in the audience.
Apologies if that does not tick the boxes for political correctness, but with Ruby Wax at her frankest and most forthright, I think we can get away with it.
She is talking us through her battle with bipolar disorder - what they used to call manic depression. And it's seriously funny. Serious because Wax is passionate about lifting the stigma. And funny because she makes her living doing comedy and she is extremely good at it.
On nose jobs, for example: "From ethnic to Aryan in a hammer blow." On Madonna: "A rented African kid is like a Gucci bag, but easier to carry."
Fame and fortune offer no immunity from mental illness, as she knows from personal experience. One in four of us will suffer from it, she tells us, several times. And many of them are in the audience, it becomes clear, when she takes questions after the performance. Yet for 20 years she was in denial.
Now she's fully "out". And it is because she wants to make mental illness "acceptable" - together with an unashamed desire to make some money - that she has turned it into a stage show.
"My mind derailed but I got a show out of it," she says. "You're paying for the therapy!"
She and musician and singer Judith Owen, who suffers depression, took their show to a dozen Priory clinics before going on tour across the UK - it has been to Sheffield and Glasgow, Brighton is coming up - and plan to take it to prisons.
Wax realised as a five-year-old that she didn't know "how to live life". Her childhood was blighted, and she was cast as loser. She got her own back by getting famous. But the cracks began to show, TV became her drug of desperation and by the interval she has reached the part of her story where she has started to lose it.
She no longer knew whether to have a manicure or jump off a cliff so she was hauled off to a clinic for dolphin music and farmyard therapy, while concerned friends helpfully urge her to "perk up".
Her constant refrain is that there's no manual for life - no manual for being a kid, no manual for adolescence, for becoming a wife, for being a mother or for facing the dark journey to old age and beyond.
But Wax - born to a Jewish sausage maker and his accountant wife in Illinois - opens the show by thanking the pharmaceutical companies that made it all possible.
She hit the big time with the '80s sitcom Girls on Top, then hit the even bigger time as a loudmouth American interviewing Pamela Anderson, Imelda Marcos and other luminaries. But her fame only masked the pain and one day she "finally lost the point of me" and suffered a nervous breakdown.
She is at her most moving when she re-lives her "losing it" episodes on stage. You feel - you fear - it is too convincing to be an act. And then she snaps out of it. She is just being herself - albeit a very scripted self - and it is hard to resist that vulnerability. Wax has the audience with her from the moment she starts baring her soul until the roller coaster has taken her to the very depths, and back up again.
Maybe it is a kindred spirit thing. There is a Q&A session bolted on to the end of the performance and it is clear that many of the questioners share Ruby's problems. A schizophrenic woman high up on the balcony tells us she is not taking her medication, she fears she will be sectioned and she has not enjoyed the show. But maybe that is because she is not feeling well, she adds.
At this point I cannot help thinking about the days when people would pay a penny to watch the lunatics at Bedlam as their Sunday afternoon outing. What a long way we have come in 200 years.