Tasked to expose a coin counterfeiting scheme, Luca and Isolde travel to Venice just in time for Carnival. Amid the masks, parties, and excitement, the romantic attraction between the two reaches a new intensity that neither can deny.

Their romance is interrupted by the arrival of the alchemist, who may be the con artist they've been looking for. But as Luca starts to investigate the original charge, the alchemist reveals his true goal--he plans to create the Philosopher's Stone, a mystical substance said to be capable of turning base metals into gold and producing the elixir of life.

With pounds of undocumented gold coins and an assistant who claims to be decades older than she appears, all evidence points to the possibility that the alchemist has succeeded in his task. But as Luca and Isolde get closer to the truth, they discover that reality may be more sinister than they ever could have imagined.