What threat did Mary, Queen of Scots pose to Elizabeth and Protestantism in England?

For homework! PLEASE help!!

http://www.historylearningsite.co.uk/mary_queen_of_scots.htm

Well, she killed a bunch of Protestants.

Catholic France occupying Scotland as a protestant becomes queen of England for the first time in its history? If this isn't a threat then what is?

Mary Queen of Scots was Catholic - nothing wrong what that you might think, but back then England's worst enemy was Spain - Catholic.

Queen Elizabeth I was 'protestant' and I do not mean just Church of England, she was both radical and non-conformist - and in the eyes of Spain, a Heretic.

Mary Queen of Scots was caught up in a plot to kill Queen Elizabeth I of England - she was held prisoner for a long time and eventually sentenced to death for treason for continuing to plot against Elizabeth while she was a prisoner.

This next link explains the threat posed by Mary Queen of Scots for Elizabeth.
http://www.historylearningsite.co.uk/mary_queen_of_scots.htm

Elizabeth I
http://www.youtube.com/watch?v=YtjKAqR_D3g&feature=related

She was the enemy, a Catholic

The answers above leave out crucial factors. Unless Elizabeth had a son (or even a daughter) then Mary and her issue (through Henry VII oldest daughter Margaret) were the heirs to the English throne.

Every heir was a threat to the serving monarch in those days - even if they were sons of the reigning king.

However in addition the Catholic world believed that Elizabeth had no right to the throne as Henry 's divorce of Catherine of Aragon was not sanctioned by the Pope - making his marriage to Anne Boleyn bigamous and Elizabeth illegitimate.

And to make matters even worse the heir to the throne was a queen of an enemy (Scotland) who had the backing of both France and Spain.

She therefore posed the most serious threat to Elizabeth, to an independent English nation and to the early Protestant faith.