I don’t know, she thought, I can’t tell. They look exactly the same, apart from the colour of the vests. She knew now how other people had felt when looking at the twins before they were swapped. It was eerie, how alike they were.

“Green for Riley,” said Lauren, feeling her pulse quicken but keeping her voice steady, “Yellow for Morgan.”

Lauren glanced at Pauline. When she looked back at the babies their eyes were open. She gulped back a gasp and grabbed one hand with the other to stop them flying to her mouth. Both of the creatures were fully awake and concentrating on her with a steady gaze. Baby lips pressed together, miniature hands clasped.

“Hello, there, Morgan and Riley,” said Pauline in a sugary voice. “Mummy’s been missing you. Haven’t you, Mummy?”

Three pairs of eyes upon Lauren, waiting for her response. The nurse wanted her to be insane, that much was clear. It probably made her job more interesting. But those two babies, what did they want from her? The eyes were old, full of knowledge. Her boys had crystal-blue eyes, with grey at the edges, just like Patrick. But these two pairs were starting to turn green. River-weed green.

“Yes, I’ve missed you,” said Lauren, aware not only of the eyes, but of the unit’s CCTV camera mounted in the ceiling, making her self-conscious, so that she felt forced to put on a show. She could do this. She told herself, pretend you love them, Lauren, you know what that looks like. “I don’t ever want to be parted from you again. My precious boys.”

The tears that came were real. Pauline patted her shoulder. The babies watched Lauren crying for a minute, fascinated, then turned their faces towards each other. Lauren saw something pass between them before they both inhaled and started to cry too. It was the same sound she was making. They were copying her. Lauren’s throat closed, her sobs strangled. The twins continued. That same unnatural tone.

“Hungry, are we?” said Pauline, apparently not noticing that the boys were doing an exact impression of Lauren’s soft sob, her adult cry. They didn’t sound like babies at all.

Lauren tried not to stare at them as Pauline went over to the little table by the cot where the formula and the baby bottles stood. She picked up an empty bottle. “Oh, fiddlesticks,” she said, “I need boiling water. Hang on, love.”