Mary unearths a dark secret being kept by a Spanish prince, so she seeks Catherine's counsel. Meanwhile, suspicion surrounds a new ambassador from English court; and Bash's quest to find a mysterious murderer takes him to Greer's tavern.

Claude is forced to marry someone selected by Narcisse. Meanwhile, a surprising discovery is made by Elizabeth, and it could alter her reign; and Mary asks Gideon to help her confirm her suspicions about Prince Don Carlos.

Mary's feelings for Gideon are hard to suppress, but she does her best as she seeks political allies. Meanwhile, Elizabeth and Greer face gut-wrenching scenarios; Claude is in danger on her wedding night; and a power struggle over the regency continues.

Mary must prioritize her life over her cousin's. Meanwhile, Lola and Elizabeth unexpectedly join forces; Catherine can't escape her past; and Mary and Gideon begin to see each other in a new light.