Clint didn't hear it until long after the battle, long after the screams were released, long after the terror-induced shots of adrenalin had left his body. He had thought—no, he had feared—that he would hear it again, that it wouldn't really be gone. After collapsing into sleep the night after it was all over, he had been encompassed by nightmares, with the all-powerful Cube dominating every facet.
His eyes snapped open and swept over the ceiling. As he had taught himself to, he didn't move upon awakening: that would lead to a fall straight from his suspended hammock to the uncarpeted floor below.
Everything was still and oh-so quiet, giving no hint to the bloody chaos that Clint had been surrounded by less than twenty-four hours ago. Of course he knew about the grime and gore that had been spread across the floor by his scraping feet, and the pile of equipment and armor he'd been too exhausted to try and put away. Clint nearly fell asleep down there last night. He was glad he didn't, if gladness was something he could even feel right now.
It was here in this hush, before Clint had a chance to truly rouse himself from slumber, that he heard it. The Tesseract.
He couldn't even tell what it was saying. It was just an incoherent whisper, a malicious hissing in the back of his mind.
Every muscle in Clint's body went tight and the strength of Hawkeye fell into place, fighting desperately until he realized that it was out of reach. The Tesseract couldn't hurt him. But he couldn't make it go away either.
Hawkeye stepped back, and he was Clint again. His eyes closed as he told himself not to scream. Everything was fine. Everything was not fine.
This was never going to stop haunting him. Sure, he had known the moment he had first reached himself again that his memories would shadow his life forever. But this… this was different. This was the Tesseract, the thing that tore him out and unmade him, shoving back in something else who killed without a thought instead.
And here it was, whispering in the back of his head. Forever whispering, forever reminding Clint, reminding Hawkeye too, that he was powerless.
With a growl Hawkeye sprung from the hammock, fingers grabbing the edging rope as his feet slammed against the floor.
The activity and focus for a moment were able to shut out the noise, and it was only if Clint strained to listen that he realized it was still there. While he couldn't destroy the whispering Tesseract, he could drown it out.
Clint played his music as loud as the neighbors would allow. He refused to stop moving until he fell asleep again, even though his pulled muscles and suffering joints pleaded with him desperately. The Tesseract was waiting in his dreams, however, and it showed him the most strange and terrifying things.
Clint decided he would never, ever tell anyone about this. The truth of it terrified him—he could only imagine how other people would react.