Pulling her knees up to her chest, she wrapped her arms around her legs. What have I done? She re-ran the events of the day in her mind.

She'd never worked with DS Turner before, not side-by-side at any rate. And she had heard enough from her friends who had, in full eye-rolling detail, to know that he was smug, fussy and arrogant to work with. So, having been given the assignment and after exchanging pleasantries, she listened to what he had to say, after which she just had to make a suggestion. The brown eyes had pinned her with a frosty glare. "PC Armstrong, I want you to watch... and record. And then radio in at the first sign of movement. Can you do that?"

She had done her own share of eye-rolling then. He was so rigid and fussy... and rude. She hadn't quite been out of earshot when he made that remark about her being an airhead to Inspector Weston. He had meant her to hear, she knew it.

So Sally had sat in the car next to him, doing a silent slow burn at his comments. He wasn't precisely the chatty type, so making conversation was a non-starter even had she wanted to. Sitting in slightly hostile silence, Sally had wished it had been Callum sitting next to her, or Will, or even Max Carter. Anyone but Stuart Turner. A short snatch blared through on the radio. Stuart had answered, "yes, guv." A request for him to join DI Manson around the corner.

He had looked around before opening the car door. Had turned back to her and said: "Stay put. Watch, record and radio. Nothing more."

Biting back the urge to say something rude in return, Sally just replied: "yes, sarge."

"Good." He'd slipped away, keeping to the shadows.

Sally had glared after him in frustration. Did he really think she was stupid? She was perfectly capable of following a suspect.

She sat. And waited. And idly tapped her foot against the side of the footwell. Then she saw him, the target. He looked nervous, clutching a plastic shopping bag as though it was a lifeline. No Stuart, no back-up. What had they expected her to do, lose him? Of course she was going to follow.

So she had followed him, after announcing to everyone on the radio that she was pursuing Suspect One on foot. And discreetly followed at a distance. She kept to the shadows. Hurried quietly along the hedge, tracking him. He rounded the corner, so she had quickened her pace a little. Stepped round the corner...where he was waiting for her. She had time to register footsteps behind her before she had seen the gun in the suspect's hand. A weight cannoned into her and a loud bang came from somewhere in front of her, before the weight bore her to the ground.

She sat hard down on the pavement. Stuart Turner was sprawled on top of her. He was heavy, and for a moment she couldn't think why he would be lying on top of her. She had sat up and when she moved to push him away, her hand encountered something wet. There was a rushing noise in her ears, and even though she had been able to hear the shouts of her colleagues and the pounding of feet, it all seemed far away, like above the surface of a lake she was submerged in. She knew she had pushed aside his jacket, feeling for the wound; she knew her fingers met what seemed like an enormous hole in his shoulder; she knew she followed procedure and attempted to stem the flow of Stuart Turner's blood over her jeans and shirt. But the sum of her knowledge was limited. Events were hazy, disconnected, and made no sense.

The only sense she could make of any of it now was that Stuart Turner was in surgery, after having been shot... and it was all her fault. If she closed her eyes, she could still picture his eyes glaring at her. She could still hear his voice admonishing her to stay put. To do as she was told. She hadn't. She had disobeyed him, and now he was broken and bleeding on the operating table, and it was all her fault.

She wouldn't leave him. She couldn't. She had done so much damage already. What if he died because of her? All around her people came and went. Callum Stone had accompanied her and Stuart to the hospital. As they were taking Stuart to where she couldn't follow, Stone's big hand closed over her arm. Firmly. He didn't hurt her, but she sensed he might want to. He pushed her gently but firmly into an examination cubicle. She wanted to protest.

"Stay put."

She sat. And stayed put this time. And watched. And wondered what she had done. Whether she had just killed her sergeant. And wished she could turn the clock back.

Jo, Stevie and Grace passed by her, heading towards intensive care. Inspector Weston, Callum Stone, then DI Manson, and lastly the DCI. She watched the anxious procession and curled into herself a little more.

What have I done?