What happened that the Celts believed that happened on this night?

The Celts believed that on the night of October 31, known as Samhain, the boundary between the living and the dead was blurred. They thought that the spirits of the deceased could return to the earthly realm, leading to rituals and celebrations to honor and appease these spirits. People would light bonfires and wear costumes to ward off malevolent entities, while also preparing feasts to welcome friendly spirits. This night marked the end of the harvest season and the beginning of winter, symbolizing a time of reflection and transition.