Mary was certainly accused of sanctioning the attempted assassination of Queen Elizabeth in 1586 – the infamous Babington Plot. This scheme, led by Sir Anthony Babington, planned to kill the protestant Elizabeth and replace her on the throne with the catholic Mary. The proof of Mary’s involvement with this plot rested on letters between she and the plotters, where she undoubtedly agrees to the plan. However, there has always been a suggestion that this evidence was fabricated by Elizabeth’s spymaster, Sir Francis Walsingham. The court clearly believed him, and Mary was executed for treason at Fotheringhay Castle on 8 February 1587. To the end she protested her innocence. So, as with many events in Scottish history, it depends on who you believe, and to an extent which side you are on, as to whether Mary Queen of Scots was a martyr or a conspirator to murder.
Answered by George Dalgleish, principal curator of Scottish History, NMS.