There’s no shadow of a figure in her peripheral vision as she goes about her day. No footsteps behind her in an alley as she comes home from work.

Instead, he visits her in the darkest part of the night, padding soft and deadly into her dreams at 3 a.m., when she is at her most defenceless. In her own bed.

The sleep rituals are the only weapons she has.

First, she makes herself turn off the iPad, even though she wants to watch another episode of her reality show. But the blue light scrambles your brain and keeps you awake. This is just basic advice. Next comes the bubble bath – not too warm, not too cool – with the meditation audiobook playing from the phone lying on the sink. She doesn’t really like baths; she always ends up getting sweaty or chilled, but all the advice suggests that this is the right thing to do for A Good Night’s Sleep.

That’s how she thinks of it: in capitals. A destination. The Holy Grail.

She’s drunk the mug of hot chocolate – the best part of her routine – and eaten the banana. (They give you serotonin or something like that. She’s a bit hazy on the science.)

Now for the lavender oil, which she spritzes on the pillow, but not too much because someone told her that can have the opposite effect to the one desired.

Climbing into bed, she lifts up her thriller from the bedside table and looks at the picture on the cover. It shows a woman half-turning under a streetlamp, eyes wide and startled, like someone being followed.

With a small shudder, she puts it back on the nightstand. It’s quite good, but maybe not for bedtime reading.

Instead she twiddles with the dial on the clock radio until she finds Radio 4. It’s not her thing at all in the daytime, but droning, posh voices seeping into the room are comforting at night. Someone on there is talking about moving to a Scottish island for a year and doing something involving sheep. It’s incredibly boring, but isn’t that what you want at bedtime? Excitement is not what she needs right now.

Closing her eyes at last, she pulls the duvet with its freshly changed cover up to her chin and inhales its clean scent, breathing in and out very slowly. The lamp is still turned on and the orange glow bleeds through her eyelids, but she isn’t ready to turn it off yet.

She’s not ready for the darkness.

Her parents say she resisted the lights going off from when she was a little girl, even before the night terrors began. And it only got worse.