An anonymous letter was delivered to Lord Monteagle, a catholic, on 2nd November. It warned him not to participate in the opening of the Parliament. The letter informed that an attempt on the King’s life and the lives of all those gathered in Parliament would be made. Robert Cecil, a Protestant, sent soldiers to search the Parliament. Just before midnight in the cellars near the House of Lord, they accumulated 20 barrels of gunpowder hidden under piles of coal. The soldiers also found Guy Fawkes. 
The letter warning one of the members of government to stay away from Parliament is believed today to have been fabricated by the King’s officials. On 8th November Fawkes put his signature on a confession. This confession did not name all his accomplices. On 9th November Fawkes signed another, more detailed confession with the names of all the others involved in the plot.

There are fundamental problems with the letter: it is unsigned and is very vague in its content. It says nothing about the details of the planned attack, still the King and his men knew exactly where and when to catch the conspirators; moreover, the powder they were planning to use was so old as to be useless. Since Guy Fawkes and his colleagues got caught before trying to ignite the powder, we’ll never know for certain.