Mentally exhausted, Ekki anonymously seeks quiet and 'himself' in Melkwegen priory's retreat program for burnt-out executives. However Overbeck is undercover there to train four monks in military style to take charge of security for an incognito visit by German pope Benedict to take the legendary Peace Bible to Rome. Wilsberg must join the program as cover, being called in by an anonymous monk to discretely investigate the drowning in a blue dye tub of 'cellerarius' (treasurer) monk Bertram, officially reported as simple cardiac arrest. Alex was hired by contractor Stritt as the monastery never paid the solar energy system he installed three months earlier, is denied entry as female but sneaks in, bumps unto Georg and is later discovered showering by Overbeck, so they and Ecki team up. Doctoral student Angela is allowed in the library to study the precious bibles, but hides her own secrets, which proves perilous. Shortly after, friar Ansgar is murdered in a seemingly similar way.