When Simon, an English envoy, tells Mary that the English are aware of her fragile engagement to Francis, Mary and Francis put on a show to protect their alliance.

An ex-lover of Francis' arrives and brings danger with her, so Bash consoles an uneasy Mary. Meanwhile, Queen Catherine persuades Aylee to snoop on Mary; and Bash lands in hot water with heretics, who accuse him of disrupting a sacred ritual.

An attempt to scare Mary causes Queen Catherine to take drastic measures to make sure the guilty party is caught. Francis, aware of Bash and Mary's growing attraction, turns to Olivia. Bash ventures into the woods to pay his debt - the human sacrifice the pagans demand - and returns with blood on his hands. Meanwhile, Kenna comes clean with the girls about her affair with the King, to a mixed response.

Henry returns from Rome unsuccessful, and accuses Catherine of adultery with Nostradamus with the goal of executing her. Catherine learns about Isobel's baby but the pagan mark on her foot is gone, making her useless as evidence against Bash. Mary and Bash learn that years ago Catherine had an affair and gave birth to a child before Francis was born. They inform Henry, who realizes that the father is his friend, Richard Delacroix, and has him imprisoned. Henry also rejects Catherine's attempts to out Bash and Diane as pagans, as he already knew about their heritage. Catherine has an encounter with Clarissa and, upon questioning Nostradamus, learns that the girl is a foundling who was disfigured by attempts Nostradamus' father made to remove a birthmark on her face; Clarissa is Catherine's daughter. Catherine attempts a murder-suicide with Mary, but Clarissa saves both of them, and Catherine is taken away to the tower to await her execution.

When Clarissa kidnaps the younger children of King Henry and Queen Catherine, Mary and Bash work with the Queen to find them, with tragic results. Meanwhile, when Lola attempts to help her brother with a debt he owes, Francis rescues her, causing the two of them to grow closer.