Sherlock was checking in on Mary, who had woken up briefly but not for long, when Sam Winchester called John's phone.
John answered his phone, looked at Sherlock quickly, and left him alone with Mary.
Sherlock took Mary's hand in his and gazed down at her. She was the single most important thing in John's world. She was there for John when he wasn't, she was carrying John's child, and above all else, she loved him. Sherlock had no right to come between them. But it was John, not Sherlock, who had said the words. But John loved Mary. Any idiot could see that. It would be better if Sherlock just left them alone. But he didn't want to hurt John like that again. What was he going to do?
John walked back into the room. "Sam is back at the hospital. He needs us to go get him. You coming?" he asked.
"Are you leaving Mary?" Sherlock asked.
John said, "She'll be safer here than travelling in the Tardis in her condition."
"That's not what I meant," Sherlock said.
John stared at Sherlock for a moment until a pained look filtered into his eyes. Sherlock didn't want John to leave his wife, but he didn't want John to reject him either. No good news could come from the look on John's face.
"I'm not going to leave Mary," John said, "I'm sorry, Sherlock. I just-I can't."
Well, that answered that.
Sherlock headed towards the Tardis to pick up Sam. The Doctor and River glanced over at Sherlock as he walked past them into the blue box.
John ran after Sherlock into the Tardis, and the door snapped shut, leaving the Doctor and River on the outside.
John whirled around and stared at the closed door. "Did you do that?" he asked.
Sherlock shook his head in response and tried to open the door. It wouldn't budge.
"Doctor, can you hear me?" Sherlock called.
"Yes," the Doctor said, "Open the door."
"We can't," Sherlock said.
The Doctor shouted, "What do you mean you can't?"
Sherlock said quickly, "The doors shut on their own. We're stuck."
John looked at Sherlock, worried. Sherlock didn't know what exactly was happening, but being trapped gave him a potent feeling of being in serious danger. He kept the fear from his face for John's sake.
Behind them, a light went out.
Sherlock asked the Doctor, "Don't you have a key?"
"It's not working...Cas says he's going to call Gabriel. Hold on," the Doctor said. Sherlock pressed his back to the door. As long as the Tardis didn't take off, they'd be fine.
Another light blew out, then another, and another until the only source of light was coming from the Tardis console.
"This is not good," John said.
Sherlock said quietly, "No, it is not."
"What's happening in there?" the Doctor asked.
"Something turned off the lights," John said.
The Doctor shouted, "Is there any light left?"
"Yes," Sherlock said, "The console is still lit up."
"Go there! Stay out of the shadows!" the Doctor shouted.
John and Sherlock ran up the steps to the console and stood in what little light it provided.
The Doctor's voice was suddenly everywhere as he asked, "Are you both okay?"
"Yes," Sherlock said, "What's going on? How can we hear you?"
The Doctor said, "I reworked the intercom from the outside. It's not important right now. What you're dealing with is Vashta Nerada. They are flesh eating creatures that live in shadows. How many shadows do you have?"
"Flesh eating creatures?" Sherlock asked.
"Yes. How many shadows do you have?" the Doctor asked urgently.
"One each," Sherlock said.
The Doctor gave a sigh of relief and said, "Good. If either of you get another one, tell me."
"This is insane," John said, turning to face Sherlock, "We're going to die, aren't we?"
"No, we're not going to die. They're working on a way to get us out. We'll be fine," Sherlock said.
John sighed and said, "Sherlock, you're a horrible liar." He turned away from Sherlock and accidentally stepped a foot out of the safety of the dim light.
"John!" Sherlock shouted.
John screamed in pain as the darkness swallowed his leg.
Sherlock pulled John to him and out of the shadow. John collapsed against him, eyes blown wide. He was clearly going into shock.
Sherlock looked down at John's leg when the Doctor shouted over the intercom, "What happened? What's going on?"
Sherlock's heart was hammering in his chest. It took him a moment to think. Quickly, Sherlock laid John down on the floor beside the console, making sure no part of him touched shadow. He removed his scarf and tied it high on John's thigh tightly.
"I'm sorry," Sherlock said as John cried out.
"Sherlock, what's happening?" the Doctor shouted.
Sherlock took off his jacket, wrapping it around the white bone to stem the blood flow from what was left of John's thigh. "John stepped in the shadow. His leg is gone. He's going to bleed out."
Gabriel's voice filled the intercom, "Was your birth planned?"
"What does that-"
"Cas says Moriarty called you a fallen angel. If you are, you could save John. Was your birth planned?"
"Mycroft was planned, I was an accident," Sherlock said. It was something his brother was all too happy to remind him of.
"Open the panel under the console where the most light is coming from," Gabriel said.
"No," the Doctor protested quickly, "He can't absorb the time vortex. He'd die."
"If he's an angel, he could use it as grace to heal John," Gabriel argued.
"But if he's not an angel, he'll die," the Doctor said.
Sherlock shouted, "Would I be able to save John if I'm just human?"
The Doctor said, "Well, yes, but I would really advise against this sort of risk. This is your life, Sherlock."
Sherlock looked at John. His friend's breath was coming in heaves and whimpers. He'd lost a lot of blood. Sherlock wrenched open the panel under the console without a moment's hesitation. He loved him. It wasn't a choice, it was the only option.
Sherlock stared into the bright cosmic expanse swirling within the Tardis. The tiny stars and lights enticed Sherlock to come closer. He didn't fight it. He had to save John. An infinity like Sherlock could never have imagined poured from the heart of the Tardis into his head.
It was hot. It was so unbearably hot, heat searing through his system like he'd absorbed lightning. His whole body felt like fire. The energy started at Sherlock's eyes and mouth, then slowly grew to encompass all of him as he exploded with white hot light. He felt like his essence was being ripped apart by time itself.
But he needed to stay together. He needed to save John. Everything in him screamed at him to save John.
A quiet calm fell over the inspector as he moved the lightning in his head out towards his hands. His hands glowed, and with a single thought, he sent a beam of light streaming into the Tardis, obliterating any Vashta Nerada in its path. Sherlock felt the molecules of the dark things shattered. As the shadowy swarm died, the lights of the Tardis regained the strength to light up the room.
Sherlock could see the life draining from John. He could see his energy, his essence, collapsing and flowing out with the blood. Placing a hand to John's chest, he used the power of space and time to heal John's leg as if the Vashta Nerada had never been there to begin with.
John gasped and sat up, looking at his leg. "How did you-?" he said, "I thought the Doctor said something about you dying."
"I took the time vortex into my head," Sherlock said.
John stared at him, wide eyed and said, "Don't you dare die, Sherlock."
Sherlock grinned, knowing his eyes were glowing rather than his hands, and said, "Not dying. Looks like I'm a fallen angel."
John said, "Yes, as if you needed to add to your ego. Just in case you're not an angel, you should really put that back."
Sherlock felt the energy start building in his head again and had to agree. He looked into the console, forcing the energy to surge back into its place in the Tardis.
Once it was out, and Sherlock was back to normal, his head felt empty and dark like there was too much space left.
"Well, I'm not dead," Sherlock said.
"So, you're an angel. What does that mean?" John asked.
Sherlock shrugged. He didn't know much about angels aside from Gabriel and Castiel, and he barely knew them.
An excruciating pain shot through Sherlock's head and down his spine. He cried out in pain, falling back onto the floor.
"Sherlock!" John shouted.
The Doctor finally got the Tardis door open and ran in towards the console.
Cas rushed to Sherlock's side and touched two fingers to Sherlock's forehead. The pain stopped as Sherlock lost all consciousness.