Before Jam begins, the audience sees history teacher Bella Soroush (Jasmine Hyde) still in her classroom in the early evening, trying to settle down to mark essays but distracted by her uncomfortable shoes and stuff in her bag, and unable to fully relax and concentrate. We get the sense that she’s been in this state for a long time, always slightly on edge.

Enter Kane McCarthy (Harry Melling), a student she last saw 10 years ago at a different school. A student she’ll never forget and is still scared of. He just wants to talk, he says. He’s dying of a brain tumour and just wants to sort out what happened back then, he says. Except, he’s got a baseball bat and a large backpack with him, and this really doesn’t look good.

Kane has ADHD and comes from a difficult background but has the sort of charisma and daring that would have made him a legend at school, the lynchpin in a gang of teenage troublemakers, scourge of the teaching staff. It’s hard to imagine Kane having a good relationship with any authority figure, or any authority figures having a good relationship with him, but things went particularly sour with Bella. Over the next 90 minutes, Matt Parvin’s script slowly reveals why.

Kane was very good at getting under Bella’s skin. It started with low-level pranks in class and taunts that she had big teeth. It progressed to racist smears and Kane implying that Bella liked telling poor white people like him what to do. Bella dealt with it as best she could.

Now, with Kane in front of her and she in front of him, they both have a chance to justify what they did on that day when it all came to a head and they both ended up in hospital, and, ultimately, each at new schools. Then there was the time four people came to Bella’s house, damaged her property and left racist messages on the walls. She’s sure one of them was Kane and she wants him to confirm it.

As the details emerge and are relieved, Kane seethes that Bella ultimately outwitted him, getting back her life while he has almost nothing, oblivious to how he made her suffer and how hard she must have worked. Harry Melling skillfully conveys Kane’s mood swings and hyperactive, inarticulate rage.

Bella, meanwhile, must confront that she wasn’t blameless in all this and that the career she’s clawed back could be over if anyone ever starts believing Kane over her. In Jasmine Hyde’s performance is the sense that this will never be over.

This is difficult material, and lesser actors would struggle to convey to the audience why Bella doesn’t just run away and call the police as soon as possible, or that Kane is at least partly sincere in wanting to settle the matter. You can’t take your eyes off either of them, and Jam is gripping, although it lets itself down towards the end in a scene where Bella and Kane re-enact their fight.

It doesn’t entirely work and it’s hard to understand why either of them would get sucked into this sort of roleplay. As a consequence, the ending of the play seems unsatisfying, although it, unlike the re-enactment, has a reality to it.

Whatever the truth of what happened between Bella and Kane back then, it’s clear that this is something they can’t resolve or ever feel comfortable about. And as an audience member, you are left with much the same feelings about the play.