The assignment was simple: Infiltrate SHIELD.
The plan was simple too: Get on their radar, let them send an assassin, catch him off guard, and never lose the advantage again.
Americans never did understand mind control. They pictured military prisons, torture, repeated mantras about eternal loyalty to some political ideology. Rubbish. With all their bombastic posturing, they lacked the subtlety to properly appreciate her skills. That made them weak.
They sent some sharp-shooter with a bow. No need to waste the big guns on her. Captain America was needed elsewhere. Typical American hubris.
He spent a week scoping her out. Following her around to learn the pattern of her movements through the city. Deciding which rooftop would provide the best vantage point for bringing her down. At least they'd had the sense to tell him not to get close. Not that it would do him any good.
She was careful to set up a regular pattern. Let him get comfortable. Let him think he would know where and when to expect her at any time. She knew which rooftop he would choose before he did. He never did have much choice at all.
So when the day came when he was ready to make his move, she was one step ahead. She was in the building before he was on the roof. She would wait for him to check his watch, then attack. Break the pattern, bring him down. Easiest thing in the world.
He put up a decent fight at first. She hadn't expected a sniper to be so good in close range. No matter. She caught him off balance, caught his arm before he could finish falling off the roof, and told him to sleep.
He went down easy. So willing to relax, to believe the fight was over, to let himself feel safe. She had just saved his life, after all. And you can trust someone who just saved your life, can't you?
She embellished of course. Made him forget that she was the one who had put his life in danger. That had obviously been the seedy mob boss he'd seen her with on Monday. She didn't trust him, followed him, betrayed him. Saved Clint's life. Clint was so grateful that she had saved his life. He couldn't bear the thought of taking hers. Sure, she had made some mistakes, but hadn't we all? She had the makings of a good agent. "Agent Romanov," that sounded good. He would like to call her Agent Romanov. He trusted Agent Romanov. Agent Romanov had saved his life. He would like to make a place for Agent Romanov at SHIELD. Agent Romanov would be good for SHIELD. SHIELD could trust Agent Romanov. It made him happy to think of her as Agent Romanov, trusted SHIELD operative. He had no reason to think of her in any other way.
Sure, he had originally been sent to kill her. But that just didn't feel right somehow. In the end, he made a different call.