Katie Burns lived in an apartment building haunted by the ghost of Henry H. Holmes.
One night, the lights started to flicker in Katie's apartment. When ectoplasm dripped onto her shoulder, she went over to the light switch and found goo oozing out of it. She looked inside of the switch and screamed when she saw H.H. Holmes looking back.
By the time Sam and Dean Winchester arrived to investigate, unwittingly accompanied by Jo Harvelle, they were told by the building manager that Katie had skipped out about a month before, without paying him rent.
It was unknown exactly what happened to her, but it's assumed that she was killed, considering there were human remains in his lair that could possibly have been hers. Also, she fit the physical description of all of the women that H.H. Holmes' spirit had victimized during the building's history.