Vespers Rising is a book that serves as a transition between the first and second series.
It has four stories: Gideon Cahill, 1507; Madeleine Cahill, 1526; Grace Cahill, 1942; Amy and Dan Cahilll, Present.
Rick Riordan, author of The Maze of Bones, made Gideon's tale. It narrates the tragedy of the fire on Cahill island, and Olivia's mourning for her perished husband.
Madeleine's story was created by Peter Lerangis, author of One False Note and several other books. It tells of Madeleine's attempts to reunite the shattered family, and how her first encounter with Damien Vesper inspired her to form the Madrigal branch.
Grace's own first mission is told in her tale. It says how she discovered Gideon's ring and how she defeated George S. Patton, a known Vesper.
Amy and Dan's story narrates their discovery of the ring and their first encounter with two Vespers.