A dream vacation. A perfect anniversary. A killer hiding in plain sight. When Derek and Brianna Murphy set off on a romantic river cruise from Passau to Budapest to celebrate twenty-five years of marriage, they expect historic cities, candlelit dinners, and a much-needed reconnection. What they don’t expect is the instant bond they form with two other couples—strangers who, over shared excursions and late-night conversations, begin to feel like lifelong friends. But friendships forged on calm waters can shatter in dark depths. On the final morning in Budapest, the body of a passenger is discovered drifting in the Danube—an apparent accident that quickly proves anything but. When Peter Andrassy, former NYPD detective turned investigator for the Hungarian National Police arrives, he is tasked to untangle a web of secrets that followed the tourists ashore. Can Peter find the killer and bring them to justice? Or will he become a victim himself?