Spirited Vesper Holly has crossed mountains on camelback and narrowly escaped earthquakes. But even she is surprised when President Ulysses S. Grant appears on her doorstep and asks for her help.

Notables from around the world have come to Philadelphia for the Centennial Exposition of 1876. Also attendance, however, is the notorious, evil Dr. Helvetius. And only Vesper can thwart his most insidious, ingenious, and far-reaching scheme ever...