“Good. Fast as you can, please. Her gases are crap, and she usually responds well to that.” Harriet’s expression gave nothing away as she listened to Jem’s chest and cast an eye over the monitors.

“Please don’t…” Jem kicked with her feet, trying to sit up properly. “Don’t—I’m okay.” She started to cough, collapsing back against the pillow as sweat beaded on her hairline.

“Last resort, Jem,” Harriet said. “And we’re not there yet. Let’s see how you are after the magnesium and an hour or two on CPAP. Does that sound all right?”

Although Rosie had no idea what bargain had just been struck, some of the tension eased from Jem’s posture. The nurse connected a small IV bag to one of the lines and adjusted its flow.

“Lovely, thank you,” Harriet said. She slung her steth around her neck. “Goodness, Jem, you’re making my eyes water. Shall we get you into a gown while we set the CPAP up? Officer Jones?”

Rosie all but snapped to attention, supporting Jem as the nurse dispensed with preliminaries and cut Jem’s uniform away. The gown went on before her boots and trousers came off. Rosie tucked a blanket over Jem’s bare legs, mortified on her behalf, though Jem seemed resigned, or perhaps accustomed, to the indignity. The mild effort of moving knocked her sats again, and Harriet wasted no time placing a large plastic mask over her face, securing it with two thick straps, and activating the machine its hose was attached to.

“I’ll check your gases again in an hour and we’ll go from there,” she said as the machine began to work in synch with Jem’s breathing. “I think CPAP warrants a call to your parents, don’t you?”

The mask precluded any debate on the subject, but Jem showed no sign of dissent. Harriet pulled her mobile from her pocket, checking the monitors again as she did so. “Your sats are already ninety-one. Why don’t you shut your eyes for a while so you don’t scare the pants off your dad when he gets here?” She wrote a note on Jem’s chart, waiting until Jem had slipped into a doze before she went over to Rosie. “Sit down before you fall down, and stick your tongue out for me,” she told her, attaching a probe to Rosie’s finger.

The adrenaline rush that had seen Rosie through the last couple of hours seemed to abandon her abruptly. Too bewildered to protest, she followed the instructions, her backside hitting the chair hard as her legs folded beneath her.

“Lower your head.” Harriet placed a hand between Rosie’s shoulder blades. “It’ll pass.”

“Will she be okay?” Rosie mumbled, studying her boots as they blurred and sharpened again. “And what’s CPAP?” She felt like an infant, full of questions but only capable of articulating them in the simplest terms.