Short answers, pulled from the story.
Mary, Queen of Scots was executed on the 8th of February 1587 after being convicted of plotting to assassinate Queen Elizabeth I of England. Evidence against her came from intercepted letters, deciphered by Elizabeth's spymaster Francis Walsingham, which showed Mary had sanctioned the Babington Plot to kill Elizabeth. She was tried before a court of 36 noblemen at Fotheringhay Castle in October 1586 and beheaded the following year.
Mary, Queen of Scots was held captive in England for eighteen and a half years. She arrived in England in May 1568 after escaping Lochleven Castle and crossing the Solway Firth by fishing boat, and she was executed in February 1587. During that time she was confined to various castles and manor houses including Tutbury Castle, Sheffield Castle, and Chartley.
Mary, Queen of Scots had three husbands. She first married Francis, the Dauphin of France, in 1558; he died in December 1560. She then married her half-cousin Henry Stuart, Lord Darnley, at Holyrood Palace on the 29th of July 1565; he was found murdered in February 1567. Her third marriage was to James Hepburn, 4th Earl of Bothwell, in May 1567, a union that led directly to her abdication and imprisonment.
The casket letters were eight unsigned letters, two marriage contracts, and sonnets purportedly written by Mary to the Earl of Bothwell, which were used as evidence that she was complicit in the murder of her husband Lord Darnley. The originals, written in French, were possibly destroyed in 1584 by Mary's son James. Historians including Antonia Fraser, Alison Weir, and John Guy concluded they were either complete forgeries, contained inserted passages, or were written by a different person, while Jenny Wormald and some contemporaries accepted them as genuine.
Mary, Queen of Scots was the great-granddaughter of Henry VII of England through her paternal grandmother, Margaret Tudor, the elder sister of Henry VIII. Many English Catholics considered Elizabeth I illegitimate and viewed Mary as the rightful queen of England as the senior surviving legitimate descendant of Henry VII. Henry II of France formally proclaimed Mary and her husband king and queen of England in 1558, though Parliament had excluded the Stuarts from the English succession under the Third Succession Act of 1543.
Mary, Queen of Scots was beheaded at Fotheringhay Castle on the 8th of February 1587. She wore crimson brown beneath her outer garments, the liturgical colour of martyrdom in the Catholic Church, and her last words were in Latin: "Into thy hands, O Lord, I commend my spirit." The executioner, Bull, failed to sever her neck with the first blow, striking the back of her head instead; the second blow completed the act. When he held her head aloft, the auburn hair fell away, revealing that Mary wore a wig and had very short grey hair.