Twinfinite: “While the games core narrative is solid fantasy fare, there are plenty of intriguing side quests to be discovered off the beaten path and one of the more confusing ones is A Thief in the Night. So, with that in mind, for those wondering how to complete A Thief in the Night in Hogwarts Legacy, heres what youll need to do.”
Source: N4G PC Hogwarts Legacy A Thief in the Night Side Quest Guide