Guy Fawkes was a Roman Catholic soldier in England in the early 1600s who was unhappy with the Protestant monarchy. He joined a plot led by Robert Catesby to blow up the House of Lords during the State Opening of Parliament using 36 barrels of gunpowder, with the aim of assassinating King James I and replacing him with a Catholic head of state. The plot was discovered after an anonymous letter warned Lord Monteagle not to attend Parliament that day. Guy Fawkes was found in the cellar under the House of Lords with the gunpowder and arrested. He and the other conspirators were tried, convicted of treason, and executed.