This is an old story. Ilka is a girl with twenty sheep. One evening she walks home across the frozen lake. Her grandfather says, "Never cross the lake at night." But Ilka is late.
Fog comes. She cannot see the shore. The ice cracks! Ilka stands still and listens. Far away, a bell rings. She walks to the sound, and the ice is strong. At the shore, the old bell hangs on a post. Nobody is there. Her grandfather comes with a lantern. "I did not ring it," he says. "Nobody did."