The Duke of Norfolk wanted to marry Mary Queen of Scott's, but Elizabeth didn't allow it so two catholic Nobel men lead a plot to replace Elizabeth with Mary.
Throckmorton Plot 1583
The Papal bull was a special message from the pope, which excommunicated Elizabeth from the Catholic Church. This was published by Pope Pius V on the 27th of April 1570. This made Elizabeth angry, and Catholics had to decide between the Pope and the Queen.
Babbington Plot 1586
This plot was an invasion from the Netherlands to replace Elizabeth with Mary through murder, so she could marry The Duke of Norfolk. The plot was exposed before it could be completed.
Essex's Rebellion 1601
This was another plot to replace Elizabeth with Mary. Once they killed Elizabeth the plan was for the French Catholic, Henry Duke of Guise and an uprising of Catholics to invade. But the plot was discovered and Throckmorton was executed.
This was an attempt of treason to replace Elizabeth with Mary, led by Anthony Babington. It was the discovery of this plot that lead to Mary's trial and execution.
Execution in progress
Essex was given a role to defeat rebellion in Ireland, instead he made a truce. Elizabeth was furious and removed his wine monopoly. So he marched to London with other courtiers to take Elizabeth prisoner. His route was blocked and he was executed for treason.