There was a sharp knock on her door. Louisa took a hand towel from the bathroom, placing it over the spilled water, before opening the door.

‘Thank God for that.’ Tiff, her face serious and completely free of make-up, stepped inside the room and closed the door behind her.

‘What are we thanking God for?’

‘For you being in here.’

‘Where else would I be?’ A knot of worry began to tighten in her already painful tummy.

‘I lost track of you last night—’

‘What do you mean, you lost track of me? Didn’t we just get back here together?’

‘You don’t remember?’

Louisa’s initial worry-knot grew in size and intensity, the sensation increasing the sick feeling. No, she didn’t remember.

‘I’d had a lot to drink … I think I have you to thank for that.’

‘Sorry, you know what I get like after I’ve had one too many – I’m pushy.’ Tiff smiled apologetically and sat down on the bed beside Louisa.

For most people, having a lapse in memory after a heavy drinking session was funny – an expected side effect that gave rise to mickey-taking from others who had witnessed the drunken antics. But for Louisa, any gaps in memory only added to the dread that it was happening again. A period of her life during her last year of college was a complete blur to her – not just a day or two, but a huge chunk. For a long time afterwards, Louisa had experienced regular panic attacks, often for no apparent reason. The distress of why she couldn’t remember often overwhelmed her.

Her mum had pushed for her to see a doctor, saying it wasn’t right for a healthy teenager to have such debilitating attacks of anxiety. Louisa had only agreed on the premise that she could go on her own – not wanting her mother to know what might be causing them. Deep down she’d known that something bad had happened to cause them; there’d been a trigger – but she’d pushed it to the back of her mind until her mum had forced the situation.

The doctor had said stress was a factor for the panic attacks, but in relation to the missing chunks of memory, he’d mentioned something called dissociative amnesia. This in itself had caused more stress than if she’d not gone to the doctor at all. He’d talked about how someone could block out certain information because they’d suffered a traumatic event. Louisa had obsessed about this, gaining as much information about it as she could through library books and journals at the time, then looking up everything about it online years later. The memory loss associated with the disorder included gaps in memory for long periods of time, or of any memories that involved the traumatic event.