Stone arrived back at the office bearing a couple of bags, one from Subway and the other from Greggs the bakery. "I got us lunch," he told Burke, who was going through the latest information from the forensics team. "I got a meatball marinara sub and a Belgian bun for you."

Settling himself in his chair, Stone took out his own lunch, a turkey, ham and cheese sub, and was about to take a bite when Burke stopped him.

"You might want to hold off on that, Collins wants to see you."

"What about?" Stone asked, reluctantly re-wrapping his sub.

"I don't know for sure, but," Burke lowered his voice, "Justin went to see him after you left to take Mrs Cromwell to the hospital – he was in with Collins for a while and when he came out he was looking very pleased with himself, the way he does when he thinks he's got one up on someone."

"I must have hurt his feelings," Stone remarked, giving every appearance of being concerned. "I guess I'd better go and see what the boss wants." He caught the satisfied look on Mason's face as he passed his subordinate's desk but ignored it.

"Steven said you want to see me," he said after being invited to enter the DCI's office.

"Yes. Have a seat, Nate," Collins told him.

Stone knew his superior well enough to know that he wasn't in all that much trouble - Collins never invited someone to sit if he was going to bawl them out.

"I had Mason in here earlier," Collins said after a few moments. "He isn't very happy with you."

Stone gave an amused snort. "He never is."

"True," Collins agreed. "But on this occasion, I think he may have cause. Mason claims you are trying to steal the hit-and-run case from him – that you spoke to a Mrs Cromwell this morning, who should have been dealt with by him."

Stone had to resist the urge to laugh; it was a bit of an effort, given how amusing he found the suggestion, and it showed on his face.

"I'm glad you can see the humour in this, Nate," Collins said. "Perhaps you'd like to tell me what happened."

"Sure. Mrs Cromwell was in reception when I arrived this morning; Sergeant Frost had tried to get hold of Justin but couldn't, so he asked me to have a word with her, which I did. By the time I discovered she could identify the gentleman who was knocked down on Sunday night, Justin had arrived. I could have let him take over, but Mrs Cromwell is an elderly woman, and I thought it best not to confuse her.

"Besides, would you really want Justin dealing with an elderly woman? She was only here to help us and her neighbour by doing her civic duty; he'd have left her feeling as though she was a suspect."

Collins nodded. "That's true. He's never been the gentlest of people when it comes to questioning. So, was she able to make a positive identification?"

"Yes. His name's Alan Bollard and he lives at Forty-Seven Foxholes Road, which, according to the map, is just two streets away from where he was knocked down. He has no enemies, no family in the UK, no nothing really. According to Mrs Cromwell, he's just a nice old man who likes to make himself useful to his neighbours. She doesn't know for sure, but she thinks he was out with his dog at that time of the night because he has difficulty sleeping, he's on medication that keeps him awake, and walking Daisy helps.

"Oh, and she's agreed to take Daisy so we don't have to keep her in the canine unit. I've given Justin all of this information, so he's up to date."

"From the sounds of it," Skinner said, "Justin's making a fuss about nothing, like usual. I'll have a word with him. In the meantime, you'd better get on with your own investigation. I want to hear you're making progress, and are getting ready to make an arrest."