A gallery in the palace of Westminster.
After an intense prelude, the curtain rises on a festive chorus of courtiers awaiting the Queen, who soon enters. Elizabeth is perplexed however, for she has received a proposal of marriage from the King of France but is in love with the Earl of Leicester. Lord Talbot reminds her of the wretched fate endured by Mary Stuart, Queen of Scots, held prisoner at Fotheringay Castle; whereas Lord Cecil, invoking reasons of the State, advises the Queen to have no mercy on her enemy. Leicester now enters. After a brief encounter with the suspicious and jealous Elizabeth, he remains alone with Talbot, who tells him that he has been to see Mary and has received from her a portrait and a letter addressed to him. Leicester is perturbed and moved, for he secretly loves the Queen of Scots. He is about to leave when Elizabeth appears. He tries to intercede with her on Mary’s behalf, but succeeds only in exacerbating the Queen’s jealousy. She nevertheless agrees to meet her enemy in person.

The park at Fotheringay.
Under constant watch, Mary Stuart enjoys a breath of freedom in the park at Fotheringay, where her thoughts turn nostalgically to her youth and to the now distant “fair shores of France”. Suddenly a chorus and a hunting fanfare are heard. Elizabeth and her retinue approach. A duet between Leicester and Mary delays the fateful meeting between the two queens. But now Elizabeth enters with her numerous courtiers in attendance. She treats her rival with haughty contempt even though Mary has prostrated herself before her. Whereupon the Queen of Scots rises and reacts by insulting Elizabeth in front of all: an offence that can by now only render inevitable the sentence to execution of Mary Stuart.