April showers bring mystery when a stranger leaves Jan and Elaine a package containing a valuable first edition of Henry Wadsworth Longfellow's Evangeline. The cousins discover that it once belonged to their late grandmother, and a cryptic note in the book uncovers a family mystery with implications in the present. The cousins take the book to Bristol Payson to learn its value, but when the torrential rains cause the Bookworm to flood, the book is stolen. The cousins set out to recover it, assisted by Elaine's visiting daughter, Sasha, and Elaine is chagrined when Sasha begins spending time with one of their prime suspects. Elaine and Jan visit Lancaster's Department of Public Works to be sure their drainage system is adequate to prevent flooding. There, they find an ornate chandelier, about to be discarded, and install it at Tea for Two. But when the chandelier explodes, their investigation of its origins -- and how it got to the public works building -- takes them to an abandoned old mansion with a puzzling past.