Those that linger and /or are stuck remain as ghosts until someone like me finds them and releases them.

I live in a small city that is now part of the Northern California Wine Country. Before wine became fashionable this town was known as the slave capital of the west. Native peoples and Hispanics were sold as slaves. Many people died in this valley. Besides wine there are many ghost here. Through the mid to late 90s I participated with other people and some Spirits too in freeing thousands of people who were ghosts over to then other side.

If higher spirits (ones that have successfully passed or Angel-types) or people like me don't help them then they remain ghosts.