When Mandie, Celia, Jonathan, Mrs. Taft, Senator Morton and Uncle Ned leave Italy, they know that the house they are traveling to in Switzerland is surrounded with mystery. The very ancient, very large chalet they will stay at has unusual things going on that no one has been able to figure out.

Could the rumors and tales surrounding the chalet possibly be true? What about the singing that is heard late at night, but in unintelligible words?

Strange as well are the servants and some of the other quests at the chalet. What's really going on here?

A fine setting for Mandie and her friends to work on another mystery!