The song here is "A Modern Myth" by 30 Seconds To Mars
A Modern Myth
Castiel could hear the commotion; Micah was missing and the angels knew Clara had done something, despite her returning Metatron to them, unharmed. The minute they had Metatron back in their possession, he insisted that he was Micah and that they had killed the real Metatron. The angels were certain that, despite he had no physical abuse, Clara must have driven him mad.
They had some angels trying to find Micah, but they had no information. They couldn't sense him or use anything that could locate him. Trying to find Micah was the equivalence of explorers trying to find the lost city of Atlantis.
It was a great risk, but Castiel was back in Heaven, trying to see for himself. He was tired of just standing still while time passes, while things happen and he can't help. He was tired of being useless and pushed aside. He wanted to see if Metatron was telling the truth because it sounded strange; too strange to come from him.
Castiel had passed a few angels in the pristine corridors of Heaven and, if they had recognized him, they said nothing. Every step he took felt like he was sneaking in without anything to hide behind. Basically, he was, but exiled or not, he was an angel and all angels can call Heaven their Home.
The closer he got to the cells, the more he encountered angels and then he was one corridor away. He nearly succeeded, but that would have been too easy. As he approached the cells, they began to recognize him. Some had stepped in his way and two held him back. He didn't resist them, but he searched for someone whom he could talk to.
A middle aged woman stepped up and her eyes were hard and her lips were tight, in a straight thin line. Her whole expression was hard and impersonal, and Castiel knew she wasn't going to be divulging any details.
"Castiel," she said as she stared at him with those hard eyes. "You were exiled. You have either courage or stupidity to return." She added and she glanced at the angels holding him back, as if ready to tell them to dispose of him.
"I wish to see Metatron." he said and she looked back at him, her expression unchanging. "He might know where to find Micah." He added and she stared at him like he was crazy.
"If he had, he would have told us. He wouldn't wait to see the likes of you." She said and then the two angels grabbed his arms, ready to escort him out of Heaven, when behind the solid doors to the cells, a deep roar echoed. Everyone remained still and they heard it again. Metatron was bellowing and then it became clear; he was calling for Castiel.
"Please." Castiel said with softness and patience.
The angels glanced at him, as if contemplating on ignoring Metatron, but they released him and watched him as he hesitantly walked towards the large solid doors. He pushed them opened, ignoring all the angels behind him, watching him, and walked down the dark hall of cells. He could see Metatron's face pressed up against the bars of the furthest cell, but nothing about him seemed like himself as he approached.
"Castiel! Castiel, please listen to me. I'm not Metatron. I'm Micah. The others won't believe me." he said and Castiel could see the mixed emotions in his eyes. He was desperate, scared, confused and panicked. "Clara killed Metatron and Gabriel made me to look like him. Please say you believe me." he said and Castiel approached with an expression of confusion himself.
As crazy as it sounded, Castiel knew he was telling the truth. Metatron would never appear so desperate to convince someone of his lies. He could leave you with doubt and uncertainty, but he would appear like this. The expression in his eyes was haunting, as if he was driven mad, but he wanted someone to believe him. There was fear in his eyes, perhaps fear of what he had seen if it had involved Clara, the Cambion Queen of Hell.
And the fact that he knew about Gabriel… no one but Castiel knew about Gabriel.
As Castiel looked at Metatron, he knew he was telling the truth; he was Micah in disguise, under the guise of Gabriel's twisted trickery.
Now, Castiel had to ask himself why. Why would Gabriel do this along with Clara? Why would he allow Metatron's death and why would he make Micah take his place? There had to be a reason and before Castiel can free Micah, he had to know.
"I believe you, Micah." Castiel said and the angel in the cell was relieved. The worry lines on Metatron's face relaxed and there was a glimmer of relief in his eyes. However, he couldn't free Micah until he spoke with Gabriel. "I'll go get help." He said and then Metatron was worried once more.
"No, don't leave." he said, his hands reaching out of the cell with desperation.
"I won't be long, Micah. I promise, the angels will know the truth and they will help." He replied and walked away, as hard as it was to ignore Micah screaming for him to stay, afraid that he'd be in that cell for all of eternity.
As he walked away, he realized that he most likely delivered an empty promise. He couldn't guarantee that the angels would believe him or help Micah. Most importantly, he couldn't guarantee that Gabriel would undo whatever it was he did. He seemed to have placed his loyalties to Hell, so the chances of him helping Micah were probably non-existent.