A glass of clear liquid, but it is not water. When it stirs (when someone slams a door, when someone hesitantly picks the glass up) the liquid becomes opaque and whatever’s in there spins around nervously. “Drink it,” she says. “See what happens.”
The other one picks up the glass and meets the eye of the thing inside. “Sorry,” she mumbles, then she opens her mouth like a yawning hippopotamus and pours all of it down her throat. A few swallowing noises come from the space where she used to stand. “What happened?” she asks, for a moment visible again.