Audrey’s throat narrows and her hand tightens around Zoe’s fingers.

Ten years she has had to love her little girl; to protect her, comfort her, laugh with her, take pride in her. Ten years to wipe away her tears, sing her to sleep, kiss her scraped knees, bathe her fevered brow. Ten years to teach her to walk, talk, run, jump, paint, draw, sing, skip, read, write. But now a rogue collection of blood cells over which Audrey has no control is stealing her away.

Ten years: a lifetime and yet the blink of an eye.

Zoe’s eyelids flutter and the muscles pull taut across Audrey’s chest, a feeling she once thought might have been hope but which she now understands is simply love.

She remembers how, when Zoe was younger, she had always wanted to climb trees that were too tall for her. I can do it, Mummy, I know I can. Audrey had always capitulated eventually, letting Zoe climb a little way up, hovering underneath, her hands outstretched ready to catch her should she fall. And then, when the girls were older, it was always Zoe—not Lily or Jess—who climbed the highest: fearless, athletic, nimble Zoe. The child Audrey had once believed to be invincible.

Audrey glances at the clock on the wall: a quarter past six. She has promised to collect Jess from Emily’s house before seven and she is already at risk of being late. But she does not want to leave before Zoe has woken up.

Audrey is grateful to be here alone today. Most days Jess accompanies her and sits by the bed of her twin sister, reading to her or relating anecdotes from school, the resemblance between the once-identical girls now just a faint echo. It has become a strange after-school ritual the three of them share, one that Audrey worries may not be good for Jess, but the girls have been inseparable for a decade and it is painful enough that they no longer share their days, their nights, their hopes, and dreams without denying them this hour each afternoon too.

All three sisters had been so close, once upon a time, before Zoe’s frequent spells in the hospital cut short their childhood. Her three musketeers, Audrey had called them. On Sunday afternoons they would perform musicals for her and Edward—Annie, The Sound of Music, Bugsy Malone—all under Lily’s careful direction, seeking out costumes from the dress-up box or the back of Audrey’s wardrobe, outfits she hadn’t worn for years and couldn’t remember buying. Jess would invariably forget the words or the choreography and Lily would get cross with her until Zoe would leap to her twin’s defense, point out that it was supposed to be fun, tell Lily to stop being mean. But to Audrey it was perfect whether or not they were in tune or in time.

Had Audrey known what would happen later, she’d have recorded every single minute of it on film.

Audrey looks down at her daughter lying under anonymous hospital sheets and wonders, not for the first time, how it is that the fate of a life—the fate of a family—should swing on an imperfect collection of blood cells, invisible to the naked eye.