"What do you mean?" Sherlock asked the computer, his voice slightly strained. "Euthanized? You've got it wrong. John is not the Companion Cube."
"When a Companion Cube is not present," said the computer, "Another candidate must step forward. Please escort your Companion C-" There was a moment where the voice malfunctioned, but a second later it was back. "-your John to the Aperture Science Emergency Intelligence Incinerator."
"No," Sherlock said simply. "What if I refuse?"
"The testing cannot continue until your John has been euthanized."
"Then the testing will not continue," Sherlock said simply. "Come along, John. There was a room back in the chamber, and I thought I saw some food. We can survive on that long enough until I can find a way for us to escape." He started to walk back to where they had come from.
John looked back at the incinerator. "Could we just drop something else down?"
Sherlock scoffed. "Oh, no. She's much too clever for that. And with all these security cameras around? Unless you can find me a mannequin, a wig, and a jumpsuit she'll never be convinced that you've fallen into that incinerator." Sherlock reached the edge of the platform they were on, and dropped down. Even now, he still expected to crumple to the ground, and felt odd when his legs reacted as if he had only fallen a foot or so. This did not hinder him for long. He slid past a slightly raised wall panel and found himself in the room he had glimpsed before, that John had simply walked past.
It was full of writing on the walls, similar to the chamber with the gun-robots. But this time, there were pictures of a pink and white box all around. There was a heart on each side, and in many instances the box had wings. Cans of paint, still half-full, littered the floor, as well as cans of beans and makeshift plates. Sherlock was just getting a better look at where the mysterious test subject had scrawled "the cake is a lie" when he heard John enter the room behind him.
John glanced around. "Sherlock, this is-"
"-Just like the other room, yes. Lamentations of lack of cake and all." Sherlock ran a hand over the words. The paint had long since dried. "The only option is to stay here. There seems to be some kind of food, even though this place looks as if it might be very boring."
"Not where I would have picked to spend my holidays," John muttered.
The days passed unbearably slowly, particularly for Sherlock. He had taken to drawing on the walls with the cans of paint, using his hands because there were no brushes. Ignoring the computer telling him he was defacing the test chamber, Sherlock drew murals outside of the room where they were staying as well. objects from 221B cluttered the walls - his old skull, lab equipment, a violin, an old armchair. Occasionally drawings of people showed up, at first sloppy but increasing in skill as Sherlock went on. John, Moriarty, himself - these people also decorated the test chamber walls around them, Examining the drawings one day (at least, he assumed it was day - John was unclear of the passage of time), John could imagine London with such clarity that it hurt.
They had taken to sleeping next to each other. The test chambers were too-clean and too-empty. Any company was welcome.
So when Sherlock woke up one morning, he knew immediately that John wasn't there. Sherlock bolted upright at once. All the murals inside the room had been painted over in white - in black, in John's handwriting, were the words: Destroy her, Sherlock.
It did not take the world's only consulting detective to know what had happened. Sherlock ran, faster than he could remember running before. Faster than he had run when he and John had chased that taxi...
Sherlock portalled up to the platform above him and jumped across the smaller platforms until he reached the stairs. As he climbed them, the button came into view. Piled on it were all the things that had been scattered through the small room - bean cans, paint cans, pieces of computers. These miscellaneous objects were several feet high, and just barely enough to weigh down the button.
"John! You can't!" Sherlock yelled. There was still a chance... John might not have jumped yet. "JOHN!" Sherlock ran through the short hall, and his eyes fell on the closed incinerator before jumping to the now-open door that led to the elevator.
"Please proceed to the next test chamber, subject name here."
-a long, long time later-
Sherlock whirled around just in time to see the door close. He didn't have a clear picture of it, since his eyes were still protesting about the sudden amount of light they were being exposed to. And Sherlock could barely feel amused by the fact that the entrance to Aperture was merely a shed, because he was outside, outside, at last.
He was in a field - long grass around, as far as he could see. Sherlock would have preferred to be in London, of course, but the sight of anything vaguely organic -not the stark white of the test chambers- was a relief.
Of course, London might not even be there anymore. He had apparently been in suspension for a very long time.
There was the sudden sound of clanging and banging from inside the shed, and Sherlock tilted his head to one side, raising the portal gun. There was nothing he had encountered in Aperture thus far that made this much noise.
A second later, the door burst open and John stumbled out. Covered head to toe in dust and dirt, long-dried blood soaking one side of his test subject uniform, he looked a wreck. He looked up at Sherlock and shook his head. "You would not believe the time I've had."