Although details are unclear, there is evidence that in 1577 Oxford attempted to leave England to see service in the French Wars of Religion on the side of King Henry III. Like many members of older established aristocratic families in England, he inclined to Roman Catholicism; and after his return from Italy, he was reported to have embraced the religion, perhaps after a distant kinsman, Charles Arundell, introduced him to a seminary priest named Richard Stephens. But just as quickly, by late in 1580 he had denounced a group of Catholics, among them Arundell, Francis Southwell, and Henry Howard, for treasonous activities and asking the Queen's mercy for his own, now repudiated, Catholicism. Elizabeth characteristically delayed in acting on the matter and Oxford was detained under house arrest for a short time.