A middle-aged, middle-class woman sits in an armchair, an oriental rug rolled out beneath her sensible shoes-clad feet. She is composed as we enter the room, all cosy, despite a pervading air of disappointed resignation. But as Woman shares her tales and memories, ever so slowly, it dawns on you that what passes for disappointment in fact masks derangement.

Ronnie Dorsey’s new one-woman play, astoundingly performed by Yvonne O'Grady, is seriously disturbing. At first, it seems to be a mundane tale of marital disintegration, but Woman’s estrangement from her children and the rest of the world is a result of deep and lacerating wounds. Without giving too much away, you should know that this is a play about paedophilia and retribution – and absolutely not for the faint-hearted.

Woman’s crimes, both those committed by and against her, are at first only hints dropped between comments on gardening, poetry and inkwells from the Catholic school desks of her youth. But their full horror is revealed with gathering pace, and in sometimes sickening, detail: the rose motif on a screen behind her blossoming into meaning.

Perhaps the most shocking thing about Of Sound Mind is the reference in the press release to it being “semi-autobiographical”. I wouldn’t want to have lived through anything contained in this play – and yet I am grateful that something good, a fine and utterly compelling piece of drama, has come out of something so awful.