Originally, Chang was but a Chinese peasant farmer who discovered Greel, who had escaped to this time period in a time cabinet. Believing Greel to be the god Weng-Chiang, Chang hid him from Imperial troops, and later became the leader of the Tong of the Black Scorpion, a cult devoted to doing Greel's bidding. Greel granted Chang mental powers "undreamed of in this century", amongst them hypnosis, telepathy, and telekinesis. Chang used these abilities as part of a magic act in London, where he was publicized as a "master of magic and mesmerism". During his performances at the Palace Theatre in Limehouse, Chang mesmerized his audiences by reading minds and levitating young women above the floor. Unbeknown to anyone, Chang was using his on-stage persona as a cover while he lead the search for Greel's time cabinet. Chang's secondary duties included attending to his master, who hid in the basement of the Palace Theater, and to procure young women to replenish Greel's bodily degeneration. During his act, Chang would hypnotize women who volunteered to participate, causing them to mindlessly do his bidding once the show was over.
Once the Doctor began to investigate the disappearances of women in the area, Chang tried to kill him on the behalf of Greel, both directly and through the Tong. His repeated failures in this respect earned him the wrath of his master, who summarily dismissed him. As a penalty, Greel secretly hid the body of a dead theater custodian inside Li H'sen Chang's magic box, which later tumbled out on-stage in front of Chang's stunned audience. Chang quickly fled the scene, but was cornered by the Doctor and threw himself to the giant rats living in the London sewers (their size increased by Greel).
The rats ravaged him and tore off a leg, but Chang survived. His loyalty to Greel quickly turned to hate once he realized that it was Greel who ruined his performance. Chang later surprised the Doctor and Leela by greeting them as they arrived at the Tong's hideout. As he smoked opium to dull the pain, he explained how he had come to meet Greel and helped smuggle him out of China. He lamented that he would have been scheduled to perform at Buckingham Palace for the Queen before dying of his wounds.