The Craghold Curse by Edwina Noone (Belmont Tower Books, 1972)

This book is a weird mashup--combining ghosts, gangsters, G-men and some kind of demonic desk clerk!  When I saw it in the Green Shed I just had to buy it:

 

A "holiday of horror" --well, we've all had those.  You flight is delayed.  The airline loses your luggage.  The air-conditioning in your hotel room fails, and it rains the whole time you're away...

Oh.  Not that kind of Horror Holiday?

HORROR HOTEL

Craghold House had much to offer as a resort.  It was a picturesque area surrounded by Craghold Lake, Goblin Wood, and the Caves of Hex.  It was an area rich in legends of doomed families, curses and ghosts.  Theresa Galliani and her father would take a vacation here like no other--a vacation at Craghold House.

How could anyone resist a resort like that?