When the Winter Soldier sensed that he failed his mission and made his escape, Natasha immediately ditched Steve and chased after the assassin, breaking through any windows in her way. She vowed that she would not lose him this time. When they both found themselves on the top of a building, she called out to him to wait, not wanting to see him disappear from her again. Although he didn't recognize her voice, he turned around to walk closer to her, as if he was curious to see what she wanted. She fought him because there was no other way to communicate with him. When he almost killed her, Natasha was sure that she was going to die. Instead, she saw a flash of recognition cross his face, and he had fled from the memory of her. She didn't give up, and continued to chase after him, leaping off buildings as she did so.
But it was after this moment that Steve finally caught up to her, warning her that Nick Fury had arrived. It was too late to save their mutual friend. They would have to try again later.
"No," she fought Steve, "no, you can't say that!"
As she was held back by Steve, Natasha's eyes followed the trail of the Winter Soldier as he slipped away again. She wanted to feel something, but she couldn't. When Nick Fury gave her an earful about being so reckless, she didn't say anything. When Steve found a quiet moment to reassure her that they would save Bucky/the Winter Soldier next time, she didn't cry.
She simply didn't do anything.
Natasha only waited until she returned to the agency, where she found a quiet area in the building to let her frustration flow down from her dark eyes.
"Are you okay?"
Of course it's Clint Barton who asked her this; he always knew where to find her. She felt guilty for not telling him about the Winter Soldier, but besides Steve, she couldn't tell anyone. How can she do that when she doesn't know if the Winter Soldier will be dead or alive the next time she finds him? Besides, if she ends up dying for this, there's simply no point to explain anything. But Clint just looks at Natasha innocently, waiting for an answer. He's always so patient and understanding about the things she says and doesn't say, and she finally just rushes straight into his arms and breaks down into sobs.
