While it is established that copycat killer "The Scalper" was recreating a series of murders from the 1920s (and earlier), it is never really clear how does he know of the earlier murders or what significance they hold for him.
Marcus Korolus only appears briefly in this episode. The "Watcher's Chronicles", texts created as supplementary material for the series, fleshed out his backstory. Korolus was once a sane man and an immortal actor, active since the 2nd century. In the 17th century, Korolus was accused of witchcraft and burned at the stake. It was his own mortal lover Lenora who had betrayed him to the authorities. The painful experience and the betrayal made him snap. He killed Lenora in revenge, and scalped her. But it was not enough for him. He spend 300 years recreating her murder, by killing and scalping women who resembled her and had Lenora's long blonde hair. In effect killing Lenora numerous times.