He'd been having it a lot lately. A nagging feeling, a can't-quite-catch-it, on-the-tip-of-my-mind, slight, sort of, i'm-probably-just-being-paranoid feeling. Of de ja vu.

The day would start off a bit wrong, a bit tired, a bit been-there-done-that, a bit i'm-sure-i-already-drank-this-tea-didn't-i?-well-obviously-i-didn't. And it was never anything he could put his finger on. Maybe he was just getting old.

But then the day would develop into a drama, and there would be bits of the drama that made him puzzle and draw back, and think - there's something not right here. I've dealt with this case before. I've solved this problem before. I thought I'd finished with this.

No one else had noticed, or if they did, they didn't say.

The tea spilt a little as he opened the cell door, but he hoped Doctor Smith wouldn't mind.

The Doctor lay flat on his back with his hands behind his head and his long left leg crossed over his right. His eyes were closed, and didn't open when he said, "Constable Hollis. To what do I owe the pleasure?"

Reg closed the door to just ajar behind him.

"I brought you some hot tea - here, and there's sugar as well if you want it."

"Thank you. Much obliged."

The Doctor sat up to receive his tea.

"D'you mind?" asked Reg, and sat beside him. "I wanted to ask you something. If you don't mind."

"Not at all. What is it?"

"Well I was wondering, is it possible that the temporal recursion loop is somewhat haphazard? By which I mean, that it fluctuates in strength, thus allowing for some temporally localised events that have no subsequent repetition? Only I've noticed some things never changing while others change very rapidly."

The Doctor was pleasantly surprised to have a receptive audience at last. "I should say so," he said. "Yes, I think that would be possible. Particularly when the energy source is unreliable, such as the one the Master was tapping into."

"So would it be correct to say that the loop operates as a field of probability, rather than a simple linear process?"

"Exactly right."

"Oh. That's very interesting."

The Doctor regarded Reg curiously.

"I say, old chap. Do you think you could see your way to getting me out of this cell?"

"Well, sir, I—"

"Please. Most people call me the Doctor."

"Oh, Doctor, is it? Well, no. I don't have the authority to do that. That would be up to CID."

"How unfortunate."

"Yes, it is rather. But on the bright side, while you're here I thought I'd take the opportunity to discuss some possible candidates for who is the Master in disguise, so to speak. I tried to show this to CID, but, well, they were following up other leads I suppose."

Reg gave the Doctor the page of notes that he had carefully retrieved from Smiffy's bin.

"Excellent," murmured the Doctor, reading down the page. "Hollis, I believe you've just saved me a very large amount of time and a good deal of hard labour."

"The list is in order of priority, from most likely to least likely suspects. This name at the top is the one I'm really most interested in, and you can see why."

"Thank you, old man. Where would I be without you?"

"Well actually. If it weren't for me you'd most likely not be under arrest."

"Quite true," agreed the Doctor amicably. "But things always happen for a reason. Obscure though it may be."

Reg considered this. "That's a very mystical position for a person of your intellect, I would have thought."

"Not at all. Since the beginning of time, the universe has been built on the complex interplay of primary forces and universal laws. The complexity makes it nigh impossible to calculate the exact path leading up to any particular event. Nonetheless, the universe is little more than a very complex machine."

"Oh, do you think so? Only I've read recently that the relationship between that which we call cause and that which we call effect is not always as deterministic as the rational sciences have traditionally held."

The Doctor, at that point, had to tug on his earlobe. "Touché," he said. "I can see I've underestimated you, Hollis."

"Oh," said Reg dismissively, forgivingly. "Never mind. It's not as though you'd be the first."