Francis makes a surprising move after being threatened by King Antoine; Bash and Kenna's marriage is in trouble; Leith makes a discovery about Greer's new career path.

Mary must marry again in order to help Scotland, whose welfare she has to prioritize over her heart. Meanwhile, Catherine is accused of poisoning Francis, but Mary believes Catherine is being framed by Narcisse, who's angling to become regent of France.

When Mary is presumed dead, Elizabeth asks for Lola's help in taking the Scottish crown for herself; James must defend Mary's throne from John Knox; Mary faces Francis's killer.

When Darnley gets a surprise visitor, his marriage to Mary hangs in the balance. Elizabeth learns her attempt to stop Mary backfired. Meanwhile, Catherine and Narcisse find King Charles and must convince him to return to the castle.