Lestrade sighed and checked his notepad again. He'd called Sherlock in on the case because the forensic team was getting nowhere, and they needed a fresh set of eyes.

A man's body had been found in a flat, when his parents grew concerned that he hadn't be phoning them back. There was no evidence of foul play, but the flat had been locked from the inside, and the colour necklace that identified the man as having met his soulmate had been ripped off his neck and tossed aside.

In short, they had nothing.

Sherlock's tirade about evidence and footprints, and some other things that Lestrade hadn't quite caught, had taken them to the small lot next to the building, beneath the man's second story window.

Sherlock broke off mid-sentence, ranting about rain and leaves, and suddenly dropped to the ground, pulling the attention of Lestrade. God, if he forgot to eat again and passed out from low blood sugar or low blood pressure or something else just as stupid I swear I will-

His train of thought ended suddenly when he saw Sherlock was still conscious, but looking entirely... blank.

"Sherlock, are you alright?"

The man blinked, but didn't seem to recognize that he was being spoken to.

"Sherlock?" Lestrade said again, louder this time.

Sherlock looked at him, as if he'd forgotten he was there.

"Are you alright?"

The man could only shake his head. He looked utterly destroyed.

"What's wrong?" Lestrade probed. Sherlock state was unsettling, and he was starting to feel uneasy.

"I..." Sherlock started, and got lost somewhere along the way. Lestrade waited patiently as he came back to himself.

"I... can't see colours anymore," he whispered, and the confession seems to take everything left from him.

Lestrade's heart sank. If Sherlock had stopped seeing colours, if his world had gone back to black and white, it could only mean one thing.

John had died.

It was a universally recognized fact that when someone met their soulmate, whether romantic, platonic, or somewhere in between, that their world would cease being in black and white alone, like it had been since birth, and would begin to appear in colour.

Lestrade knew there was a scientific explanation behind it, but had forgotten it. Sherlock would know, of course, but he was in no state to be explaining how the eye and brain worked.

People who could see colour were colloquially referred to as 'chromes', and would wear the necklace that identified them as such. It wasn't a huge deal in society, but it was relevant for some things. Pilots had to be able to see in colour, as did taxi drivers.

It varied widely among people, how the colour appeared. For some, it would take days after they met their soulmate for the colour to seep into their world, so slowly that sometimes they wouldn't notice it. When it was slow in arriving, it was difficult to figure out the person who caused it, which generally led to frantic searching. There were websites devoted to tracking down soulmates, and books on the subject. It was a big deal.

(Sherlock could have made a fortune if he went into the matchmaking business, but Lestrade knew he loathed it, and stuck to the more interesting cases. Like murder.)

He knew for a fact that when Sherlock and John met, their worlds exploded into colour violently. It sounded like a remarkable experience. He was one of the ones that it took days to get coloured, and he may have also been quite drunk during that period. (He was coming to realize that his wife was likely not the one.)

Similarly, when a soulmate died, the survivor would no longer be able to see in colour, and their world would return to black and white. This usually happened faster than the colours appeared, but still could take a day or so.

Lestrade suspected that for Sherlock, much like the appearance of colour, Sherlock experienced a rapid and violent disappearance.

No wonder his legs gave out.

Despite the fact that there was a unit on the police force that was devoted to looking into colour disappearance and the death of soulmates, Lestrade hauled Sherlock into his car and began planning.

"Where was he going?"

"Shopping," Sherlock whispered.

"The Tescos near your flat?" Lestrade asked, and Sherlock nodded in response.

Lestrade sighed. "Okay, here's what we're going to do. I'm going to call around, see if anyone knows everything. We're going to go to Tescos, see if we can find anything out, and then we will check the hospitals. Alright?"

Sherlock only stared blankly ahead, offering no protest, and Lestrade could only assume that meant he was fine with the plan.

He picked up his radio, noting that Sherlock was twisting his necklace between his fingers anxiously.

Lestrade received a text from an unknown number. It told him where John was, at a hospital near their flat.

He told Sherlock so and set off.

They were both quiet on the way to the hospital. There was nothing to say.

At A&E, Lestrade pulled rank and showed his badge, pulling Sherlock through the doors into the heart of of the ward. A doctor came to speak with him, and he sat Sherlock in a chair out of earshot before listening.

"I'm with the police," he told him, flashing his badge again, "And that man is the soulmate. Can you tell me what happened?"

The man wasn't wearing a necklace, but Lestrade knew it was common for doctors not to. The softness in his eyes hinted that he did have one, waiting in a locker somewhere for when he finished dealing with other people's pain and suffering.

"John Watson had collapsed and was brought in by ambulance. He wasn't breathing on his own. We intubated him, and did a number of tests, including a brain scan, and we've concluded that he had a ruptured aneurysm. It's not uncommon for these things to go unnoticed if they don't cause any problems, and then they simply burst."

He glanced off to the waiting room where Sherlock sat.

"Unfortunately, shortly after that, his heart rate became erratic, and we couldn't get it stabilized. We did everything we could, but I'm afraid he died."

Lestrade blinked at the man. He knew it was coming. He knew John was dead.

And yet, the words didn't want to make sense. His brain was willing to ignore them in hopes of something, anything else.

"Thank you," he said finally. "I'll tell him. Will he be able to..." he trailed off, not wanting to say it.

The doctor seemed to understand. "He can see him, spend time with him, whatever he needs. I can put you in touch with a counselling service, and we have a soulmate department within the hospital as well."

Lestrade nodded. "I'll let you know."

Blinking to clear his eyes, Lestrade set off to have the worst conversation of his life, to tell Sherlock the truth he already knew, and probably didn't want to accept.

Sherlock was sitting in a corner chair, looking at the floor like it held secrets. Lestrade sat diagonal to him, their knees touching.

"Sherlock," he said carefully.

"I don't..." he began.

He blinked, and shook his head instead of finishing his sentence.

"They said you can go and see him. Spend as long as you'd like with him."

Sherlock blinked underneath his hair, and Lestrade didn't miss the tear that fell to his lap.

"How? Did someone... was it murder? Was he attacked?"

Lestrade shook his head. "They said it was an aneurysm. It's not uncommon," he echoed, "for them to go unnoticed, and then..." he trailed off, not wanting to say it.

"No," Sherlock said. "That's not right. An aneurysm? No."

Lestrade hesitated. "Sherlock-"

"No!" he bellowed, standing up, pushing away the arm that Lestrade tried to place on his shoulder.

"You're wrong," he insisted. "You're wrong. They're wrong. John wouldn't do that to me, wouldn't just... die like that. You're wrong. Someone did this, you have to go, and arrest them or kill them or something!"

He collapsed to the ground for the second time that day, sobs wracking his body.

Lestrade's heart ached for him.

He crouched on the ground next to him, and hugged the rocking ball of detective.

"It doesn't make sense, does it? That John could survive so much, getting shot, and running around with you, and everything, and then die from something that you never knew was there?"

He felt Sherlock nod in his embrace.

"And it's not fair, because with everything you two did, it was something so simple and mundane and unexpected, and you couldn't prepare for it or prevent it or protect him from it."

Sherlock nodded again, his sobs silent now.

"They're just... gone," he whispered.

Lestrade nodded. He couldn't imagine. Sure, Sherlock had gone so long without having colours that he'd learned to live that way. He'd never lived any other way. But after having them, going back to black and white would break him.

It was such the perfect metaphor though, such an elegant and cruel metaphor.

That the one you loved, in whatever way, because in the end it didn't matter, that the one you loved brought colour and light into your life, and took it away with them when they went.

After a while of being crouched together on the ground, Sherlock seemed to run out of tears, and he went to see John, leaving Lestrade in the waiting room that was painted grey. He wondered if that was on purpose, so that loved ones couldn't realize their soulmates had died.

The funeral was later that week, and it was lovely. Most of the people that Sherlock worked with at NSY came, so many army buddies, fellow doctors, peoples he'd saved. Hell, even Sherlock's entire family came.

Lestrade didn't miss that Sherlock had slipped John's necklace into his pocket at the hospital, and was wearing both of them underneath his scarf.

Lestrade knew how much of an impact John had left on Sherlock. He'd shown him a world of colour, and in return, Sherlock had shown John a world that was worth being coloured. Of course, Lestrade never expected it to end like this, John gone first from something so mundane as an aneurysm. He, like Sherlock, had wanted to arrest someone, punish someone for the death of such a good man.

And he, like so many others, were sure that the two would go out together, possibly in a blaze of gunfire and glory, their necklaces shining like the stars Sherlock didn't care for.

Instead it ended with Sherlock bearing both, and not shining nearly as brightly.

Sherlock didn't do any detecting work for a while. He claimed that he needed time to readjust to a colourless world, and Lestrade didn't doubt that to be true, but that was only the tip of the iceberg. He also had to adjust to a life that was missing one very essential piece. John.

When he did return, he took up more cases involving soulmates, particularly matching them up. His techniques were revolutionary, if a bit invasive and borderline illegal. People were thrilled with how often he was able to match them up. He had a success rate that rivalled the government programs that Lestrade wasn't supposed to know about. He didn't comment much on it, only commenting how much John would have liked it.

In response, Sherlock merely smiled, and asked Lestrade if there had been any nice murders lately.