From the Catholic Encyclopedia:
Layman and martyr, b. probably at Grimthorpe, Yorks, England, date unknown; d. at York, 1 Dec., 1586. From his father, Richard Langley, of Rathorpe Hall, Walton, he probably inherited Rathorpe, but for the greater part of his life continued to reside on his estate at Ousethorpe, in the East Riding. His mother was Joan Beaumont of Mirfield. He married Agnes, daughter of Richard Hansby, New Malton, by whom he had one son, Christopher (b. 1565), and four daughters. (See "Visitation of Yorkshire", ed. Foster, London, 1875.) During the troublous times of the Elizabethan period Langley gave over his energies and a very considerable part of his fortune to assisting the oppressed clergy; his house was freely offered as an asylum to priests. He even constructed a subterranean retreat, perhaps beneath the Grimthorpe dwelling, which afforded them sanctuary. This refuge was betrayed to the President of the North, and on 28 Oct., 1586, a strong band of military was despatched, several justices and ministers of the new religion joining in the quest, to make a domiciliary visitation of the Grimthorpe and Ousethorpe houses. Two priests were found in hiding at the former; at the latter Langley himself was seized. All three were carried to York, committed to prison, and subsequently arraigned before the President of the North, the priests because of their office and Langley for harboring them.During the investigation Langley was steadfast in his adherence to the Faith. He would not take the oath of the queen's ecclesiastical supremacy, nor compromise his religious heritage by seeking to ingratiate himself with the lord president or Privy Council. It was feared that the jury which had first been empaneled to decide upon the case might return a verdict in accordance with the dictates of justice, it was therefore discharged and replaced by another of tried fidelity to the prosecutors. Langley was condemned to death, without any evidence being adduced to establish the fact that he had knowingly sheltered seminary priests, and was hanged, drawn, and quartered at York. His remains were refused honorable burial, despite the importunity of his friends.
This site (thanks to Christine Niles) offers illustrations to supplement the text. Langley clearly risked everything to protect priests and thus receive the Sacraments. But that was a felony, not an act of treason--so why he was hung, drawn, and quartered isn't so clear (perhaps he not only refused to swear the oath but named Elizabeth a heretic or schismatic). The detail about the jury is important--the prosecution did not really have the evidence to convict the martyr, so they had to find a more willing jury to convict the martyr! He still had friends who were brave enough to ask for his remains; this demonstrates again the strength of Catholicism in Yorkshire, which extends well into the reign of James I.
The identities of the priests captured with him is also unclear.
Pope Pius XI beatified him among many others in 1929.