Disclaimers-JKR/WB/Bloomsbury et al own the characters. Prose and idea is the only thing I can claim.
She Fled
Lily heard James yell for her to flee, but she didn't want to leave her son at the mercies of that madman. She rushed into the nursery and was about to lean over the cradle to pick him up when he came.
He told her he would let her live if she stepped away from her son. The only remainder she now had of James. Lily didn't believe him until he raised the wand and pointed it at her chest. She saw the murderous gleam in his eyes and without a second thought, walked away.
"You chose well." He told her as she walked out of the nursery with her back straight and her head held high. She was glad, in a sick way that he waited until she was out of the room before raising his wand and uttering the spell.
She braced herself for the inevitable sound of Harry crying out his last and the sound of his triumphant laughter. But all that she heard was a roar of the most furious outrage that was followed by an explosion that knocked her onto the ground in the hallway.
Lily lay still, her red hair a cloud of tangles over her face that she didn't dare push away lest she caught his attention. She lay still, her breathing loud and hoarse in her own ears and waited for the final blow to come. But after she had lain there for what felt like hours, she then realized that no one was coming. She let out a shaky breath and pulled herself up to her knees. She pushed her hair out of her face and got herself to her feet. She felt that she didn't have any control over her own body as she found herself going to what had once been a nursery.
It was utterly destroyed. The furnishings had been knocked down by the force of the mysterious blast and the carpet had been reduced to cinders where he had stood. The crib had been knocked on its side and there was a small whimpering noise coming from what looked like dirty rags on the floor.
Lily let out a quiet sob as she knelt down and picked up the bundle of dirty fabric up. She pushed the topmost layer away and was rewarded with the sight of her son's tear-stained face staring up at her.
She walked away from the room and collapsed in the hallway. She was still sitting there, her back against the wall and her son clutched against her chest when Sirius Black showed up.
He talked about James. About Peter. How he had betrayed them all and gotten James killed. Sirius was determined to go after him and would do it as soon as he got both her and Harry to safety.
Lily had pulled herself out of her shock when Sirius said those words. She didn't care about going after Peter. What did it matter now? It wasn't going to bring James back. Besides, she didn't want to be alone with the child she held at her breast. He was something different now. Something that she couldn't comprehend. Something that would always remind her that she had failed in every way possible at being a mother. And she knew that she wasn't strong enough to live with Harry without seeing her failure in him.
At least there was someone that wouldn't see him that way and would be able to raise him without that heavy stigma. She knew that Sirius loved Harry deeply. He would take good care of him. Harry would have a good life. It would be the best thing she could do for him. Without another second of hesitation, she pushed the child into Sirius's hands.
"Take him." Sirius had blinked and had tried to refuse the snuffling child that Lily was offering him.
He protested, but Lily was having none of it and forcefully pushed the child into his arms before she turned and apparated away from him, his shouts still echoing in her ears as she did.
Ende