"Dear child," she murmured, resting a gloved hand on his cheek. "Everything is a poison, and every poison is a medicine. It's all in the dosage. Enough water can poison you. Not from drowning, no; it kills you by doing what it does, so much of it that it breaks the cell walls and dilutes the salts you need to live. And even polonium, so deadly that a few molecules can kill, has its uses."
She leaned in and brushed her lips lightly against his, gripping his shoulders hard as he stiffened and began to spasm. "Too much?" she whispered.