"Blaine, what are you doing? Get back here! Get away from that light!"
Kurt's terrified screams pierced through the room, deafening in the way the white light creeping through the crack was blinding. He was paralyzed in the doorway, instincts clashing as he fought to run from the light and save his doctor at the same time.
"Kurt, listen to me. I need you to go. Get out of this room, get out of this house, and whatever you do, keep running." The Doctor's calm voice called out to Kurt. But it was too calm, too calculated to be real. "Do you hear me? Run, Kurt, and don't look back."
He locked eyes with Kurt for a moment as he spoke the last words, a moment just long enough to give away the fear coursing through him.
"I'm not leaving you! If you get caught by the light, you'll be gone! You'll never have existed! I can't lose you, Blaine, not again."
The Doctor stopped. He was nearly to the other side of the room now, the light slowly advancing from the continuously growing crack in the wall. Kurt watched him, only now noticing the way the Doctor's whole body showed the pain he was feeling. He was no longer Blaine - young, excitable, always overenthusiastic Blaine; this man carried every year of his life as a burden, a reminder of what he had lost and what he would lose. The younger boy spoke, voice cracking though he tried to appear strong.
"And you can't lose me."
He watched as the Doctor turned to see the light progressing towards him, creeping closer with every moment he stayed still.
"This crack in the wall, Kurt," he spoke, casting his eyes downward to avoid looking at his companion. "You said it was following you."
"Yes, it has been, you've seen it - it's always there, Blaine, it's always with us."
"Us, Kurt." He briefly looked up, seeing the confusion written on Kurt's face.
"I- yes, it's with us, but you know this. Just- just come back, Blaine, I don't know what you're doing-"
"Us," the Doctor repeated, again meeting Kurt's eyes, "not you."
"What does that mean?"
The Doctor spoke slowly, almost painfully, as if he did not want his words to be true.
"When I first met you, all those years ago at your home, I told you the crack in your wall was created by two places in space and time being pushed together.
Two places in space and time that were never meant to be together."
The Doctor watched Kurt's confused expression until, gradually, his realization of the true meaning of the words changed it to one he could barely stand to see.
"No." The word came as a whisper, barely audible, and the Doctor would not have caught it had he not been watching his companion's face so closely. "No, you can't possibly mean-"
"I'm only putting you in danger by staying in your life, Kurt." This time it was the Doctor who's voice cracked, no longer able to feign composure.
"No, you- you saved me. How could you be putting me in danger when you saved me?" He broke as the words left his lips, tears falling, his whole body sobbing.
"I can't keep hurting you like this. If I go now - I'll never have put you through this, through any of this."
"You can't, Blaine! If you let the light get you, you'll never have existed, and what would the world do without you?" Kurt trailed off, turning away from the Doctor's gaze. He spoke again, directing his words not to the Doctor, but to himself, "What would I do without you?"
"I'm a Time Lord. The light can't erase me. I'll simply regenerate, start over as I have countless times. I'll only be gone from your memory." He started as he saw Kurt run to him, reaching for his hand and pulling him close.
"I can't let you go. I can't," Kurt cried into his shoulder, both their bodies shuddering with the force of his sobs. "Won't you remember me? Even if you never existed to me, you'll still remember me?"
"I could never forget you."
"Then how could you leave? How can you leave, knowing we'll never see each other again?" His words cut through the Doctor, only reminding him of the difficulty of his choice. He released Kurt, stepping towards the light that had nearly reached him at this point.
"I'll live forever, Kurt. Eventually, I must say goodbye to everyone."
The Doctor stepped forwards again, a breath away from the light. Kurt lunged forward, trying to grab onto him before he disappeared. As he moved, crying out as the light touched the Doctor, he spoke his final words to Blaine.
"I'll never say goodbye to you."