When they had almost reached their destination, John remembered all of a sudden that he hadn't warned Sherlock about the man with the umbrella yet.

"Sherlock…"

"Mmmm?", answered the young man, quite distracted.

"A while ago, a month ago to be precise, I…met a man. Well, 'met' it's rather incorrect."

Sherlock gave him a puzzled look.

"He sort of kidnapped me. Rather incorrect term too. Oh, well. I met him."

"And who was he?"

"He knew you. He said that he is an enemy of yours."

"Which one?"

John cleared his throat.

"Archenemy."

"Oh, him.", answered Sherlock completely unimpressed by the revelation.

"Do you know who he is, then?", was John's confused question.

"Yes, I do."

"And?"

"He's the most dangerous man you'll probably ever meet. But he's not my problem right now."

John's mouth fell open in a complete dazed expression.

"But…you could be in danger!", John remarked.

Sherlock simply grinned. John didn't understand and went on.

"He wanted me to spy on you."

"For an adequate sum of money, I bet. Did you accept it?"

"Of course I didn't!"

"You should have."

John was speechless, completely at loss with himself.

"So you could pay your own bills and you shouldn't always count on me for that.", the young man stated in a wider grin.

John stared at Sherlock, mouth open in astonishment, then started to laugh. It was such a carefree laugh that he almost felt overwhelmed by the sensation of it mixed with the adrenaline pumping in his blood. For the umpteenth time John thought that Sherlock was impossible. The most impossible genius, the only one impossible genius he had ever met and the only one he would have ever probably met in his whole life.

As they approached to their destination, John noticed they were aimed to Whitechapel. Twenty-five minutes later since they had left the restaurant, they got off in front of an abandoned shop. Lestrade was waiting for them just outside.

"At last! I thought you got lost!", the DI said to Sherlock.

"It's his fault.", the young man answered pointing at John "Had he not been so stubborn, I would've been here ages ago."

John was about to answer something, but let it drop, knowing it was a futile argument in that occasion.

"What have we got, Lestrade?"

"Double murder, as I texted you.", the DI said as he guided them inside the building "Two males. Discovered three hours ago by the shop's owner. He declared that the shop has been closed for three months. He came here today because a possible buyer phoned and told him he wanted to see the place tomorrow, so he wanted to check if everything were alright. And he found…that."

On the empty floor, amid the empty shelves of the shop, there were the naked bodies of two males lying on their backs. At a first glance, and at a first smell even, John noticed that one of the two bodies must have been lying there for at least one week. It was showing all the signs of the first stages of decomposition: the bloat, the blisters on the skin, the harsh smell of body fluids. As a doctor and as a soldier he was unaffected by it, but he thought that Sherlock would've been. Wrong again. Sherlock was looking at the corpses fascinated.

"What can you tell me, doctor Watson?", he inquired.

"The left one has been here for at least one week.", John answered as he approached to the bodies "The right one has been dead for…", and he stared at it "…probably twelve hours, by looking at his state. He's showing all the stages of rigor mortis and lividity, but no signs of decomposition or greenish skin colour yet. So yes, I'd say twelve, maximum eighteen hours."

"Cause of death?", the young man urged.

"Let me take a closer look..."

John knelt near the fresher victim. He looked at the head, at the chest, at the legs.

"Can I turn him? I need to take a look at his back.", he asked Lestrade, who nodded.

As he lifted the body up, he clearly saw what had killed the man. There was the evident sign of a stabbing wound just beneath his left shoulder blade, probably deep enough to have reached the heart.

"Stabbed.", John concluded "One single, very precise stab through the heart. They haven't been killed here, though. There's almost no blood on the floor."

Sherlock nodded and started his personal examination of the bodies. Like the first time, the young man moved around the corpses, focusing his attention on the right one, touched, smelt. Two minutes later he stood up.

"It will take me ages to identify them!", grunted Lestrade at some point "They are both naked and they present no recognisable characteristics. Hundreds of people go missing in London every day and they could be everyone!"

John had to admit the DI was right, it would have been a very long research.

"I wouldn't say so.", answered Sherlock.

John and Lestrade turned to the young man at the same time, both with an astonished expression on their faces.

"Ok,", said the policeman "give me, Sherlock!"

"We can narrow down the research to the City."

"Sherlock if you're making this up, I swear I'll kill you!"

Sherlock grunted in annoyance.

"Look at him! Don't you see?"

John and Lestrade still looked at each other like completely puzzled.

"First: the hair. Perfectly trimmed. By the millimetre."

"He could just be obsessed with his physical aspect.", replied the DI.

"No, no. This is a person who went to the barber once or twice a week. And look at his hands: manicured. So office work, but with a lot of customers. He didn't do this because he liked it, he did that because his appearance is his greeting card. It attracted customers. He's probably a partner of an investment society."

"That's all?"

"Obviously not. See the mark on his left wrist?"

John noticed it as soon as Sherlock pointed at it. On it there was an almost unnoticeable mark of a wristwatch.

"It's a mark left by a Panerai Luminor. They are very particular watches with a very big circular clock face. The only one which could have left that specific mark. They aren't common watches for an Englishman, so this suggests that our John Doe has got at least some connections with Swiss societies, hence the choice of a Swiss watch. Panerai are also very expensive, so he isn't an employee, he's the boss."

John looked at the young man, more and more intrigued by his brilliant mind.

"And there's the aftershave too."

"Aftershave?", asked John and Lestrade simultaneously.

"Yes, aftershave. Can't you smell it?"

"Among the miasma of a body in putrefaction?", replied Lestrade "Not really."

And John had to agree once more. He couldn't smell anything else except the harsh stink, but apparently Sherlock could.

"How could you? That's the right question!", continued the DI, addressing to Sherlock.

"I always recognise a Clive Christian 1872.", answered the young man "Every bit of this man, every bit of that smell says 'City' out loud."

"Fantastic!", John couldn't hold it anymore.

Sherlock turned to him with a perplexed look.

"Are you really keeping on saying that?", asked Sherlock.

"Sorry,", John felt quite embarrassed "ahem, I'll just shut up."

"No, it's…fine."

Lestrade interrupted their slightly odd conversation.

"So we are basically looking for a person who has been missing from the City for twelve hours."

"Correct."

"What about the other?"

Sherlock huffed in annoyance.

"It's too decomposed. But I have the idea that he's from the City too. And we're looking for a female killer."

"Female?", this time John had literally no words to describe the surprised expression on Lestrade's face "A stab like that would suggest a male, Sherlock!"

"Statistically more probable, Lestrade. But males tend to stab their opponent by fixing them in the eyes, as in a game of dominance. A stab in the back? More likely a female. Plus they are both naked, this would suggest some intimacy between the victims and the supposed woman. Plus this one is literally soaked in the aftershave, which suggests a romantic date. And it also confirms my theory about the left man working in the City. Same killer rather indicates a connection between the two."

Lestrade made a phone call and waited.

"They are sending me pictures of missing workers of the City during the last week."

When the DI finally got them, they all started to look at the screen. There were ten people gone missing in the last week. Sherlock looked at the first, second and third saying 'no, no, no', stopped at the fourth for ten seconds, but said 'no' once again. The same happened with the fifth and the sixth, but at the seventh picture he shouted:

"It's him!"

Once again John and Lestrade looked puzzled.

"No, Sherlock it isn't him.", said John quite perplexed "This man doesn't look like the one we have there."

And he pointed at the right corpse.

"He isn't the body on the right. He's the left one."

John gawked.

"The height and the weight. They correspond to those of the body. Plus he's gone missing exactly one week ago. The police thought it was a voluntary escape. I think they were wrong. The body over there is this man's. Look! There's a note under the photo!"

Lestrade clicked on the note.

"It's an alert.", he said "Someone has just reported another missing person related to him. It's his business partner."

The DI opened the photo. He was their second body.

John spent the night at Scotland Yard with Sherlock skimming through files and mumbling the whole time. When morning came he had the most precise idea of how the crimes were committed and who was the killer.

Sherlock explained John and Lestrade that five years earlier four friends had founded an investment society. Each of them had put in it a good part of the capital and the society had soon started to flourish. Despite that, three of the associates had begun to cheat and transfer some of the society's earnings in a Swiss bank. The fourth partner had discovered it and had threatened them to go to the police and confess everything. The three associates hadn't panicked and had simply thrown the man out of their society, making him lose all his money and causing his following suicide three months earlier. The man had a wife who loved him deeply and who, to Sherlock's deduction, was now taking her revenge over his husband's partners. She had already killed two, she was surely waiting for the third. Sherlock deduced that she would've done it soon, because she knew that the two men's bodies would've been probably found and she wouldn't risk her third target to suspect something.

"The problem is", concluded the young man "that we don't have a single proof against her. She's been very careful. Very, very careful."

"What do you suggest, Sherlock?", inquired the DI.

"First, don't let anyone know that the second man is missing. She'll feel safer and probably will strike soon. Second, me and John are going to follow her around. Maybe she'll make a false step. Let's go, John!"

John knew he should have said no. Yet he said nothing and followed Sherlock around London, following the murderous widow, the Black Widow, as John had named her.

They spent the whole Saturday and the first part of the Sunday on her heels, until Sherlock realised that she was going to strike that evening.

"She went to the hairdresser and bought new clothes. There's a party which our man should attend to. She's going to seduce him tonight, John!", the young man claimed at one point "She knows no one had found the corpses, but she knows they'll be found soon. She has decided for it to be tonight!"

"So we just have to wait her to bring the man back home."

"His house. She doesn't want her house to be contaminated by the men who have killed her husband. And they were too stupid to understand what she was going to do. Damn, she's good!"

"Sherlock!", John yelled at him.

"What's that?"

"God, she's a murderer and you are saying she's good?"

"Not good?"

"Really not good.", John snorted.

But the young man was right about her striking that night. At eleven p.m. she had managed to seduce the third partner of her dead husband. He brought her home and, as soon as the man was naked on the bed, she had extracted a dagger she was hiding in her stilettoes. John had to admit that Sherlock had been right even about the other point: she was good. Nevertheless, thanks to Sherlock Holmes, Lestrade took her in custody with the charge of a double and one attempted homicide.

As soon as they exited the man's flat, John noticed a figure in the distance. It took him two seconds to realise it was the man with the umbrella.

"Sherlock…"

The young man didn't seem to have heard him.

"Sherlock…", he repeated "That's him!"

"Him who?", eventually answered the young man.

"The man with the umbrella! The archenemy!"

Sherlock huffed in annoyance, as the other man approached.

"Another case solved, Sherlock.", the man said "Good for you."

"Hello, brother.", answered Sherlock heavily annoyed.

John's jaw fell on the floor.

"B-brother?"

"Yes.", replied Sherlock quietly "He's my brother Mycroft."

"Doctor Watson. I quite expected to find you here.", Mycroft replied with a smirk.

"Brother?", repeated John who was finding it hard to think "He is your brother?"

"Yes.", replied Sherlock one more time.

"Not a criminal mastermind? Not dangerous?", John was incredulous.

"He's worse than that.", the young man stated.

"Oh for god's sake, Sherlock! I occupy a minor position in the British Government."

"He is the British Government. And the most dangerous man you'll ever meet, John. And as I previously stated: not my problem right now.", the young man hissed and started to walk away.

John looked at him agape, unable to form a coherent thought.

"See you soon, Sherlock.", the man called Mycroft greeted.

"I hope not.", was the young man's dry answer.

Sherlock then followed the DI to Scotland Yard, but John, despite everything, desperately needed to sleep. He hadn't slept on Friday night, because he had been busy skimming through the two men's lives, and he hadn't slept on Saturday night, because they had been busy guarding the woman.

Now at one a.m. on Monday he was literally dying of exhaustion. And he had even lesson the following morning. He crawled home and into bed.

When he woke up at seven, it seemed to him that he hadn't slept a single second. He crawled to the university, already knowing it would have been an awful day, but blissfully unaware of what was going to happen. As soon as he entered his office with the biggest cup of coffee he had managed to find to keep him awake, he noticed there was Laura sitting at his desk.

Oh god, no. He didn't want to have any conversation that morning, let alone that conversation.

"John, we need to talk.", she remarked coldly.

John gave her a disinterested look.

"What did you do with Holmes? What case was he talking about?"

John was well aware that the conversation would have led nowhere. He didn't even think about lying this time. He went straight for the truth, hoping that Laura would have understood his point of view.

"Nothing inconvenient, Laura. He solves crimes for the police and I sometimes help him. Isn't it fantastic?", John let slip out, quite thrilled, the adrenaline still not completely vanished.

"Fantastic? It's not fantastic, John! It's sick! He's sick, he's insane!", she yelled "How could you even think of it being fantastic?"

"You don't know him at all, Laura. He's not insane! He's clever! He's amazing!"

"You're right. I don't know him at all.", she remarked quietly, but coldly "No one here really knows him. He finds it difficult even to remember the professors' names after three years! And yet he calls you 'John' and you call him 'Sherlock'!"

John felt the anger growing inside him. He knew that he shouldn't call the young man 'Sherlock', but he found that he didn't care much anymore, especially in that precise moment.

"It's not easy to stick with 'Mr. Holmes' all the time when you go around with him!", he shouted "And he…he's him! You can't expect him to behave normally! It's just that, I swear!"

"He's a bloody student, John! A student who happens to call you by your first name! It's not normal!", she shouted louder "And you even expect me to believe the 'I solve crimes with him' story? Seriously?"

"But it's the fucking truth, Laura! There's nothing else!"

"A student, John! A student! He's even got your phone number! Your bloody phone number!"

"Yes, he has! I don't know how but he has!"

And obviously it was the truth, thought John. But Laura had another opinion.

"A student with your phone number! A student who calls you 'John'! That's a thing I least expected from you!"

There was no point in that discussion. She didn't believe him and John couldn't accept that she was insulting the young man of whom she knew nothing at all. John's fury came out like a roaring cascade.

"Like I least expected you to be still in love with your ex!", he shouted.

"But it's not true!"

"Excuse me if I find it hard to believe that.", he smirked angrily.

"Is that because Holmes has told you that the other evening?", she spitted out.

"Yes, because of that.", he coldly replied.

"He's a bloody liar! Don't you see? It's just a lie!"

"I highly doubt it.", John answered firmly, before hitting his palm on the desk and shouting louder "He's always right! And if he said that, it's the bloody truth!"

Laura got up from the chair and gave John a furious look.

"I guess that's the end of it.", she hissed.

"I guess that too.", John simply replied as she slammed the door.

He hoped nobody had heard their quarrel. Luckily, at that hour, the corridor was completely empty. He collapsed on his chair, taking a sip of coffee.

He should've been sad. He should have felt something. Instead, he felt nothing. He tried to understand why. She was perfect, really. Caring, loving, passionate, clever, beautiful. She was everything a man would love to find in a woman. She was perfect.

That's when John eventually realised it. He didn't need someone perfect, he needed someone challenging. And for some odd reason the face of Sherlock Holmes appeared in his mind.