‘Over there, in that alley.’ It takes a moment for Anna to register, a few seconds when there is just a crumpled kind of bemusement on her face and then alarm. The man has one arm around the woman’s waist and he’s holding her hair. The woman is upright now but barely, her head bowed as if she’s about to throw up.

Anna and I exchange anxious looks.

Every act of violence creates an orbit of chaotic energy around itself, a force beyond language or the ordinary realm of the senses. A gathering of dark matter. The animal self can detect it before anything is seen or heard or smelled or touched. This is what Anna and I are sensing now. There is something wayward happening in that alley and its dark presence is heading out to meet us.

With one hand the man is pressing the woman’s face into the wall while, with the other, he is scrabbling at her clothes. She is as floppy as a rag doll. He has her skirt lifted now, the fabric bunched up around her waist at the back. Her left arm comes out and windmills briefly in the air in protest. Her hand catches the scarf around her neck and there’s a flash of yellow and blue pom-poms before the man makes a grab for her elbow and forces the arm behind her back. The woman stumbles but as she goes down he hauls her up by her hair. Her cry is like the sound of an old record played at half speed.

Something is screaming in my head. But I’m pushing it away. Another voice inside me is saying, this is not what I think it is, this is not what I don’t want it to be, this is not real.

The man has let go of the woman’s hair. He’s pressing her face into the wall with his left hand while his right hand fumbles at his trousers. His knee is in the small of the woman’s back pinning her to the wall. The woman is reaching around with her arm trying and failing to push him away but her movements are like a crash test dummy at the moment of impact.

‘Oh God,’ Anna says, grabbing my arm and squeezing hard, her voice high-pitched and tremulous.

In my mind a furious wave is rising, flecked with swirling white foam, and in the alley the man’s pelvis is grinding, grinding, slamming the woman into the wall. The world has shrunk into a single terrible moment, an even horizon of infinite gravity and weight, from which there is no running away. Anna and I are no longer casual observers. We have just become witnesses.