Blood
The nausea crept up her throat from the pit of her stomach; the realization that yesterday was real. She had done what she needed to, at least, that's what she told herself in attempt to consolate her conscience.
Slowly and methodically, she made her way to the bathroom sink and turned on the faucet, letting it run until steam fogged up the mirror. With hesitation and closed eyes, Cass plunged her hands into the scalding water and willed herself to keep them there until every drop of blood was erased. She closed her eyes to forget the crimson on her hands, but all she saw in her mind's eye was a sink full of reddened water.
Again, the nausea made its way up her throat, threatening to release itself. Cass focused instead on the burning water that had suddenly become cold. The image in her head changed; her hands were in ocean water now, a water so pristine and deep blue it became red. The ocean had turned to blood.
Cass couldn't forget what she had done. Despite what she told herself, she knew she had something terrible. She would have to learn to live with guilt, everyone would - if they wanted to survive.