Queen of France at sixteen and widowed at eighteen, Mary Stuart defies pressure to remarry and instead returns to her native Scotland to reclaim her rightful throne. But Scotland and England fall under the rule of the compelling Elizabeth I. Mary asserts her claim to the English throne, threatening Elizabeth's sovereignty. Rivals in power and in love, the two female regents are determined to rule but betrayal, rebellion, and conspiracies within each court imperil both thrones - and change the course of history.