The two central characters are inside, inside a cell together, but prison is also seeping into them. The guards get inside them - quite literally during the body searches; the smell and dirt gets inside one inmate, a beautician ... but Sharon, the violent, disturbed prisoner also lets music get inside her. Eventually and cathartically, she starts to get some of that inside out.
Sophie Besse has worked as a therapist in prisons and has taught drama to women prisoners. She clearly knows prison as an insider. In the play, the women guards occasionally let their guard down - they are women inside too.
There is no simplistic moralising in the play. Sharon is a tough nut, whatever she has inside, and whatever has toughened her. There are real victims to her crime. Guard number 1 puts on a protective, professional mask when she needs to - her softness is a professional weakness. And daffy Barbara may be a loving mum, but it takes Sharon to remind her how selfish she has been to her daughter.
The play ends with a redemptive scene in which each inmate acts the part of the other to an audience of just one in the cell - acting out becomes a safe way for Barbara to tell Sharon the truth about herself and vice versa. The play itself has that intimacy and urgency too - the pub theatre is minuscule, with seating for about 50 people, which amplifies the effect. What truth are we being told? Nothing simple, but nothing comforting either about how prison works - or rather doesn't.