In 1603 King James I became king and he was Protestant. The Catholics thought that king would be more tolerant of them than the previous queen, Elizabeth I, but he wasn't.
So Guy Fawkes, Thomas Percy, Robert Catesby and many more Catholic plotters met at a pub called Duck and Drake decided to kill of the House of Parliament and make King James I's daughter Elizabeth II queen.
Their plan was to dig a tunnel under the Houses of Parliament, fill it with barrels of gunpowder and blow it up. However their plan failed because the tunnel flooded as it was under the River Thames.
Robert Catesby rented a cellar under the houses of parliament and filled it with 36 barrels of gunpowder. As Guy / Guido Fawkes was an explosives expert, he was in charge of lighting the fuse.
A mysterious letter went out to Lord Monteagle about the plot so Lord Monteagle passsed it on to Robert Cecile, the king's chief adviser, who then passed it on King James. So King James had Parliament searched from top to bottom until they found Guy Fawkes about to light the fuse on November the 5th.
When they asked Guy Fawkes what his name was he said his name was John Johnson, as that was a very common name at the time. So they arrested Guido Fawkes and put him on the rack for 3 days until he confessed his real name and who he was working with then he was hung, drawn and quartered and the other plotters were found and killed as well.