The Stone, the Cipher, and the Shadows: John Bellairs's Johnny Dixon in a Mystery

A flu epidemic ushers in a plague of dark magic in this spooktastic mystery featuring teenage sleuth Johnny Dixon from The Wrath of the Grinning Ghost.

Though forty miles away, Duston Heights is not safe from the flu that's raging through Boston. When Johnny Dixon's grandmother falls ill, he's sent to live with his neighbor to avoid infection. So many locals are getting sick that school is canceled for a week, and the reclusive Dr. Abram Ashburn comes out of retirement to make house calls.
...