This movie explores the turbulent life of the charismatic Mary Stuart (Saoirse Ronan). Queen of France at 16 and widowed at 18, Mary defies pressure to remarry. Instead, she returns to her native Scotland to reclaim her rightful throne. But England is under the rule of the compelling Elizabeth I (Margot Robbie), who wishes to reduce the perceived threat from Mary. Each young Queen beholds her "sister" in fear and fascination. Rivals in power and in love, and female rulers in a masculine world, the two must decide how to play the game of marriage versus independence. Determined to rule as much more than a figurehead, Mary asserts her claim to succeed to the English throne, threatening Elizabeth's sovereignty. Betrayal, rebellion, and conspiracies within each court imperil both thrones--and change the course of history.