He grit his teeth, scrubbing his hands rough and raw. Still, he couldn't completely erase the now-faint red glove up to his wrists. He just hoped no one would suspect that it was blood.
As he exited the bar's cramped bathroom, he noticed a small, dark-haired girl sitting on the stool nearest the bathroom's door. She might have seen. He walked up to her, his hands behind his back mock-politely, and somehow flirted his way to getting her outside, getting her alone. He was taking mental notes as he followed her out. No drink in hands, didn't seem the least bit tipsy. Probably here with friends.
"How much did you see?" he asked forwardly, turning to stand in front of her. He was acutely aware of the sheathed knife in his boot, hidden under the leg of his pants. Ready to use it if necessary.
"How much did I-what?"
"How much did you see?"
"I don't- who are you?" She seemed confused.
"Good," he said. "And I guess I might as well tell you. If things get too bad, I could just kill you." He grinned, more of a smirk really, as her eyes widened.
"They call me the Doctor," he said, his voice low. "I'm a….a consulting criminal, if you will. A hired assassin. Usually hired, anyway."
"You're a serial killer?" the girl whispered, a horrified expression on her face. Then, reluctantly, it turned into a sly smile.
"Clara," she said, extending her hand. "And don't they always say, two heads are better than one? I'm smart, I promise." She didn't know why she was doing this. Heat of the moment, maybe?
It took a moment for him to understand what she'd said. When it'd sunk it, a devious look began to spread on his features. He took her hand, shaking it.
"Well, then Clara," the Doctor said. "I guess we're partners in crime."

After that, she helped him more and more, started to become the brains of the operation. Made his…missions more efficient. More streamlined, more straight-to-the-point. Less chasing and catching and hunting down. And less chance of being caught. And in a sick, twisted way, Clara began to enjoy it. She began to enjoy the sound of footsteps in dark, midnight alleys. She began to enjoy the grim sound of strangled screams from the throats of victims. The feeling of blood slick on her hands.
It was never her blood. The Doctor made sure of that. He'd sworn to protect this girl, this innocent girl with a thirst for danger.