Obsession: Toxin and Antidote

She dropped her keys on the corpse. They would be proof . . . of what? Perhaps you know.

Perhaps you know how it is to be locked into a ceaseless circle of one thought, your mind an ouroboros, a creature biting its own tail, injecting toxin with its fangs and swallowing the antidote from its own flesh. Follow the creature, follow until it is so exhausted it can no longer bite or swallow.

Come to this corpse. Consider the size of the keys. Consider the size of the stump. Imagine the tree.

Prompt: Write the next part of this story.