John Watson slowly starts his way home, or at least to the flat he currently lives in. Afghanistan felt more like home than this crappy apartment. But there is only so much you can afford in London on an army pension. Yesterday he finally managed to get a part-time job at a surgery. He has seen the pity in the other doctor's eyes when he scanned over his obvious second hand clothing and the cane and turned back on his resume. But he was too desperate for pride and at least it got him a job, something other to do than watching telly or making long walks through London. Sometimes he wonders whether his life would have taken a different turn if he hadn't pretended not to recognise Mike Stamford. But it's too late for this now and back then his pride was much more intact than it is now.

A strange noise catches his attention, but when he carefully examines his surroundings, he can't detect anything wrong. He pauses a moment, taking the time to slip his key ring over his left pointer. It's not the best weapon, but it will have to do. He also resumes his military stance, making it clear to anybody who might follow him that he won't be an easy victim. Despite the two heavy bags of groceries and the cane in the middle of the night in this part of the town.

Today his monthly pension cheque arrived and after a long day doing some locum work and an even longer week of beans on toast, he couldn't resist the temptation of a normal shopping at Tesco. He would probably regret it at the end of the month, but maybe he will be able to keep his job, that would make an okay living.

There is the noise again. This time he can detect its direction, a small alleyway. And this time the noise doesn't stop. Carefully he approaches the alley. At first he can see nothing, but then he glimpses an arm and a dangerous looking knife attached to it behind some dustbins. Without thinking he drops his bags and the cane to run to the scene.

Two men holding another, above them the third with the knife. They haven't noticed him yet. He kicks the knife out of the hand, placing another kick to the man's stomach, before he starts repeating methodically what the army had taught him for situations like that. The two others have let go of their victim, so it's now two against three. And their former victim knows how to fight dirty in hand-to-hand combat. It's over pretty soon, the thugs apparently deciding that it wasn't worth it.

John looks after them for a moment; before he turns his attention to the bloke they had attacked. In the dim light he can't see much. Tall, dark curly hair, pale skin and a posh coat. No wonder, he was attacked, he doesn't belong here.

"Are you alright?"

John can't see any injuries, but the other man is swirling around, the coat adding a dramatic flair to his movement. He is clearly looking for something, his eyes on the ground. John wonders if he should be annoyed that the guy didn't even thank him.

"Looking for something?"

"Yes."

He is not sure if that is actually an answer to his question or more some confirmative sound since the guy bends down gracefully and picks something up, putting it in a plastic bag that he has taken out of his coat pockets. When he holds it up, John recognises the knife.

"This will be useful."

Another exclamation which doesn't seem to be directed at John. Nevertheless he asks: "For fingerprints?"

The man looks up and John has the feeling as if he is under a full body scan. The man's eyes lingers a moment on his left hand and John can't suppress the instinct to clench it.

"No, but there should be residual blood from his three other victims. At least, it looks at is if it is the same weapon."

It takes a moment for John to understand the complete meaning.

"Wait, you knew the man was a murderer? Are you insane coming here alone?"

"It was the fastest way to catch him." He actually sounds surprised that John has difficulties with the concept of getting caught by a killer to prove his guilt.

"You don't even have back-up, you could have gotten killed."

"I don't need back-up, I work perfectly well alone."

"Yes, I could see that." John doesn't even try to hide the sarcasm in his voice. The other man rights himself before he answers.

"Really, doctor, there is no need for a lecture. You should probably look after your groceries, before somebody else does."

It is clearly a dismissal and followed by a dramatic swirl of his coat before he vanishes in the darkness. Dumbfounded John stares after him, before he remembers his bags. Fortunately they are still where he dropped them. He discovers at home that his eggs are broken.

Four days later he signals for the next patient, hoping for something more exciting than a snivelling nose. After the nightly incident he has scanned the newspaper for any arrests, but nothing has been reported. Or maybe he has simply missed it. But there has been no missing of the giant police raid this morning when he was on his way to work. He wonders what that was about.

The door opens and instead of the old lady or young mother that usually frequent the clinic, it's the victim from the night. In the broad light of his office he can make out all the details he has missed on their first meeting. High cheekbones under bright grey eyes, a sinful mouth. His clothes under the coat are looking even more posh than in the dark.

The stranger smiles at him and before John can say anything, he speaks.

"Hello doctor, since you are in such favour of back-ups – do you care to join me?"