This story is a sequel to Apple Bloom's Mansion

Almost one year passed since this famous night where Apple Bloom had to face a whole manor full of ghosts to save her sister and her friends. Now a professional ghost hunter, helped by her mentor professor Smart Spirit, she regularly hunts bad ghosts all over Equestria.

But one day, she learns from Diamond Cup, who went with Smart Spirit to do some research in a mysterious haunted valley named the Evershade Valley, that the ghosts of the valley, usually pacific, have suddenly turned hostile and captured the prof!

It's now up to Apple Bloom to find the origin of this hostility and to save Smart Spirit, and the valley, but she has no idea who she's up against this time.

A long time ago, a whole manor, and everypony inside it, mysteriously disappeared without leaving any trace.

But it reappeared at the edge of the Everfree Forest, and Twilight decided to go investigate followed by her friends, only to not come back. Worried, and not wanting to miss an occasion to get their Cutie Masks, the Cutie Mark Crusaders entered the manor at the start of the night, only for two of them to be foalnapped by ghosts, and for the third to barely escape with the help of an old stallion.

Now armed with the Poltergust, a powerful tool to capture ghosts, Apple Bloom returns in the manor, ready to save everypony, even if she has to fight every ghosts in this manor.

A long night of terror starts for her.

Happens between season 2 and season 3. Also possesses some Dark and Drama

The saga now has a TV Tropes page (spoiler for the whole saga).