The security of the realm is at risk. Mary Queen of Scots is believed to be at the centre of a plot to assassinate the Queen. Elizabeth I’s spy master, Sir Francis Walsingham, is anxious to incriminate her. To that end he plants his creature, Gilbert Gifford, into Mary’s household. In an attempt to obtain evidence that will incriminate Mary, Gilbert seduces Anne Bennett, one of her ladies-in-waiting. As letters between Walsingham, Gilbert and Anne are exchanged, has the spy obtained a lover and loyal supporter or a treasonous ally of Mary and her conspirators?