Leigh was a petty criminal sentenced to prison for stealing a loaf of bread. In his cell on Christmas Eve, while the guards were caroling, he was raped by five men. In one night on December 19, 1962, he killed 18 people from five different families as well as a sidewalk Santa Claus collecting charity. In December of 1963, now committed at Briarcliff, he attacked orderly Sean during a holiday photo shoot, prompting his year-long stay in solitary and Sr. Jude's proscribing any further Christmas celebrations.
In 1964 , the possessed Sister Mary Eunice released him from his solitary cell and had him dress up as Santa for the no longer verboten Christmas party. There he made a lewd suggestion to another inmate sitting in his lap before knocking Frank from a ladder and attacking him. He was subdued by Frank and sent back to solitary.
He was sent to Sister Jude's office by Arthur Arden and Sr. Mary Eunice. He pushed Jude against a desk and caned her before throwing her on the bed and attempting to rape her. Jude, however, stabbed Leigh in the neck with a letter opener that she grabbed off the desk during her caning, ending her ordeal but not his life, as he survived her attack.
Leigh helped Sr. Mary Eunice and Dr. Arden, to frame Sr. Jude for the murder of Frank McCann. He put on an act of a man seeking forgiveness and was escorted by the Monsignor to Sr. Jude's cell where he bestowed his forgiveness upon and kissed her forehead. While in the sanctuary, he thanked The Monsignor for his chance at redemption. After being baptized, he dunked the Monsignor's head into the tank. He then nails The Monsignor to the cross in the place of Jesus.
In the weeks following his escape, Emerson remained at large, a criminal hunted in five states. During his spree, he allegedly murdered seven nuns, prompting Lana Winters to contemplate a volume on his exploits entitled Santa and the Seven Nuns.
To Sister Mary Eunice: "I knew who deserved to live and who deserved to die, who was naughty, who was nice."
To a woman on his lap: "What do you say we blow this pop stand, go savage a few elves, and then suck on each other?"
To Sister Jude: "There is no God, but there is a Santa Claus!"