Watch Mary, Queen of Scots Full Movie Free Online 123Movies. Mary Stuart, who was named Queen of Scotland when she was only six days old, is the last Roman Catholic ruler of Scotland. She is imprisoned at the age of 23 by her cousin Elizabeth Tudor, the English Queen and her arch adversary. Nineteen years later the life of Mary is to be ended on the scaffold and with her execution the last threat to Elizabeth's throne has been removed. The two Queens with their contrasting personalities make a dramatic counterpoint to history.