Fawkes converted to Catholicism and left for mainland Europe, where he fought for Catholic Spain in the Eighty Years' War against Protestant Dutch reformers in the Low Countries. He travelled to Spain to seek support for a Catholic rebellion in England without success. He later met Thomas Wintour, with whom he returned to England. Wintour introduced him to Robert Catesby, who planned to assassinate and restore a Catholic monarch to the throne. The plotters leased an undercroft beneath the House of Lords; Fawkes was placed in charge of the gunpowder that they stockpiled there. The authorities were prompted by an anonymous letter to search Westminster Palace during the early hours of 5 November, and they found Fawkes guarding the explosives. He was questioned and tortured over the next few days and confessed to wanting to blow up the House of Lords.