The doctor asked for the boys to be undressed, and Harper watched Patrick fumble with the babies’ clothing, pulling the yellow vest over Morgan’s head with unpractised fingers. As he removed each item from the baby he passed it to Harper, who placed it in a labelled evidence bag. Morgan woke up when his father started to undress him, but he didn’t cry. He kicked his legs and looked amused when the doctor made a face. Riley, still strapped into the car seat, made the sea-bird sound, and Morgan copied it precisely. The doctor smiled at Patrick.

“Cute,” she said. “They’ll have their own language soon.”

“Yeah,” said Patrick, rather dismissively, as if he didn’t believe it.

Harper had also heard that twins sometimes developed a language no one else could understand. The idea of it fascinated her and creeped her out in equal measure.

Soon the boys were side by side on the hospital trolley, vests successfully removed.

“I’m just going to get them out of their nappies, if that’s OK with you, Dad,” said the doctor.

“Sure.”

The doctor raised her eyebrows at Harper, who nodded, go ahead. She pulled off the nappy tabs, then picked up the naked baby and turned him onto his front, shining a pen light all over the skin, her gloved hand gently parting folds where the chub met itself. She turned the boy back over and shone the light into his mouth. Patrick looked sickened, his lips twisted. His hand rose slowly to cover them, and Harper could see that the man’s eyes were filling up.

The doctor repeated the procedure with the other baby, placing them both on their backs, naked on the trolley before she spoke.

“I can’t see anything notable.”

“OK,” said Patrick, his voice thick, “what does that mean?”

“It means there are no signs of any maltreatment, in my opinion. No injuries,” she looked at Harper, “no, um, visible evidence of foreign objects, fluids, or matter of any kind.”

Patrick groaned, a pitiful sound of disgust and relief. He covered his eyes with his hands. When he took them away, white finger marks at his temples slowly faded. The doctor put the nappies back on the babies before she turned towards the computer and began to make notes.

“You can get them dressed now, Dad,” she said, over her shoulder.

And Patrick looked at them both, lying there, gurgling, and then he pulled from the changing bag two clean vests, one yellow and one green. He held one in each hand, for a moment stood motionless then slowly raised his eyes to meet Harper’s, who saw the panic in his face. He looked from vest to vest, from baby to baby. Which was which?

“Did you see which way round they were?” Patrick’s voice was high and quiet.