Casey was an Irish doorman at the Palace Theatre in London under Henry Gordon Jago. In 1889, Jago called him his "factotum". While in the basement one night, Casey saw a skull-like apparation. He reported this to Jago and the two went looking for the cause, but found nothing.
When Teresa was found on the premises, he tried to have her leave, but she left of her own accord, prompted through fear of Li H'sen Chang, whose picture she saw. Jago explained to Casey that the recent strange goings on were being investigated by him and an amateur detective. Casey died of fright after seeing Magnus Greel's face. While performing on stage, Chang opened his Cabinet of Death and Casey's body fell out.