"The decaying mansion is known as the old Willis place, even though no one named Willis has lived there for years.  Diana and her little brother, Georgie, know every inch of its extensive grounds.  They climb trees and swim in the pond.  And they can do whatever they want, even stay up all night.  They don't have to change their clothes, brush their hair, or go to school.  They have total freedom--as long as they don't leave the old Willis place. ...

When the Alden children go camping on Blizzard Mountain, a place said to be inhabited by a ghost looking for buried treasure, they begin to think someone or something is trying to scare them off.

While visiting a recent purchase of Grandfather's, a ghost town in the Rocky Mountains, the Aldens encounter a mystery involving a run-down motel and a woman who may be a ghost.

Travis and his sister Corey decide to boost business at their grandmother's Vermont inn by staging a few "hauntings" that soon draw tourists from across the country, but when their antics awaken a dark force, they must find a way to put to rest the ghosts they have disturbed.

The Aldens investigate the rumors of ghosts, disappearing props and a haunted seat in the Trap-Door Theater.

While vacationing at a friend's country home, the four Alden siblings try to find a long-missing, priceless brooch, while also investigating the existence of a ghostly stream.

Irish orphans Molly, fourteen, and Kip, ten, travel to England to work as servants in a crumbling manor house where nothing is quite what it seems to be, and soon the siblings are confronted by a mysterious stranger and secrets of the cursed house.

A coming-of-age tale with a spooky twist!
Maggie McKay hardly knows what to do with herself. After an idyllic childhood of homeschooling with her mother and rough-housing with her older brothers, it's time for Maggie to face the outside world, all on her own. But that means facing high school first. And it also means solving the mystery of the melancholy ghost who has silently followed Maggie throughout her entire life. Maybe it even means

...

A ghost father tells his children three frightening stories to help them go to sleep at night.

While visiting an old mansion, the Aldens investigate the possibility that it may be haunted.