Sirius Black was deemed to be a follower of Lord Voldemort and accused of being the one responsible for the deaths of Lily and James Potter along with the deaths of 12 muggles. This was untrue, for he was framed by one he called a "dear friend". He was then sent to Azkaban and was forced to face torment. This is the anecdote of the time he was imprisoned and how he escaped the horrid prison. "I think the only reason I never lost my mind is that I knew I was innocent."