Imperceptible signs

One day, I took a necklace with a hollow silver heart from my jewellery box. I gave it to my sister, telling her that this was a special necklace. Whenever she wore it, she would be protected from ghosts. She wouldn’t be able to see them anymore. She wore the necklace constantly and for the next week or so she slept peacefully through the night. But soon after the ghost returned. She would now appear in the hallway and this time she had a man with her. And so it continued.