Anthony Monday is delighted when Miss Eells and her brother Emerson invite him to spend a restful summer vacation in an old house on a desolate island. But soon Anthony finds a chest that can transport them to another world -- a horrifying place where a maniacal group is plotting the destruction of the people of Earth. Will Anthony and his friends be able to save mankind -- or will they perish in their desperate struggle?

The Mansion in the Mist (1992), by John Bellairs, is the fourth book in the Anthony Monday series.

"The late Bellairs did and excellent job with mystery/fantasy for middle schoolers. His characters have a captivating charm that adds to this spellbinding adventure...a good alternative to the Hardy Boys." - Margaret Mary Ptacek 

Toward the end of the first week of their stay, Anthony began to feel that there was something wrong about the house. Nothing that you could get a grip on, but still something, well, wrong. One night he woke during a wild thunderstorm, and the boards in the corridor outside his bedroom were creaking loudly. Lightning leapt in through the tiny window, and loud cracking peals of thunder burst overhead. But it was the creaking that bothered Anthony -- it sounded like people walking up and down. When he finally got up his courage, he opened the door and peered out. Nobody there. The doors to Miss Eell's and Emerson's bedrooms were shut, and they were probably asleep. Timidly, Anthony crept down the front staircase and peered into the shadowy living toom. As his eyes got used to the dark, he saw something that froze his blood: Someone was sitting in one of the rockers. Anthony clenched his teeth and closed his eyes. He could hear his heart hammering. Then he opened his eyes again, and a blue flash of lightning lit the room. The dark shape was gone.