In 1604 Fawkes became involved with a small group of English Catholics, led by Robert Catesby, who planned to assassinate the Protestant King James and replace him with his daughter, third in the line of succession, Princess Elizabeth.  Fawkes was described by the Jesuit priest and former school friend Oswald Tesimond as "pleasant of approach and cheerful of manner, opposed to quarrels and strife ... loyal to his friends".  Tesimond also claimed Fawkes was "a man highly skilled in matters of war", and that it was this mixture of piety and professionalism that endeared him to his fellow conspirators.  The author Antonia Fraser describes Fawkes as "a tall, powerfully built man, with thick reddish-brown hair, a flowing moustache in the tradition of the time, and a bushy reddish-brown beard", and that he was "a man of action ... capable of intelligent argument as well as physical endurance, somewhat to the surprise of his enemies."The first meeting of the five central conspirators took place on Sunday 20 May 1604, at an inn called the Duck and Drake, in the fashionable Strand district of London.  Catesby had already proposed at an earlier meeting with Thomas Wintour and John Wright to kill the King and his government by blowing up "the Parliament House with gunpowder".  Wintour, who at first objected to the plan, was convinced by Catesby to travel to the continent to seek help.  Wintour met with the Constable of Castile, the exiled Welsh spy Hugh Owen, and Sir William Stanley, who said that Catesby would receive no support from Spain.  Owen did, however, introduce Wintour to Fawkes, who had by then been away from England for many years, and thus was largely unknown in the country.  Wintour and Fawkes were contemporaries; each was militant, and had first-hand experience of the unwillingness of the Spaniards to help.  Wintour told Fawkes of their plan to "doe some whatt in Ingland if the pece with Spaine healped us nott", and thus in April 1604 the two men returned to England.  Wintour's news did not surprise Catesby; despite positive noises from the Spanish authorities, he feared that "the deeds would nott answere".One of the conspirators, Thomas Percy, was promoted in June 1604, gaining access to a house in London that belonged to John Whynniard, Keeper of the King's Wardrobe.  Fawkes was installed as a caretaker and began using the pseudonym John Johnson, servant to Percy.  The contemporaneous account of the prosecution (taken from Thomas Wintour's confession) claimed that the conspirators attempted to dig a tunnel from beneath Whynniard's house to Parliament, although this story may have been a government fabrication; no evidence for the existence of a tunnel was presented by the prosecution, and no trace of one has ever been found; Fawkes himself did not admit the existence of such a scheme until his fifth interrogation, but even then he could not locate the tunnel.  If the story is true, however, by December 1604 the conspirators were busy tunnelling from their rented house to the House of Lords.  They ceased their efforts when, during tunnelling, they heard a noise from above.  Fawkes was sent out to investigate, and returned with the news that the tenant's widow was clearing out a nearby undercroft, directly beneath the House of Lords.The plotters purchased the lease to the room, which also belonged to John Whynniard.  Unused and filthy, it was considered an ideal hiding place for the gunpowder the plotters planned to store.  According to Fawkes, 20 barrels of gunpowder were brought in at first, followed by 16 more on 20 July.  On 28 July however, the ever-present threat of the plague delayed the opening of Parliament until Tuesday, 5 November.

Question: When did Wintour and Fawkes return to England?
Answer: April 1604

Question: Robert Catesby led what group of people?
Answer: English Catholics