It is Nick Knight's new partner, Det. Don Schanke, who notices that each in a series of homeless people who have been murdered has recently given blood at the bloodmobile. Eventually, the detectives determine that one of the technicians, Donald Fenner, has been murdering homeless people who might have been the source of the contaminated blood that killed his mother.
This plot element in the premiere is copied directly from the original pilot for Forever Knight, which was set in the U.S. It remained unchanged when the television series was moved to Canada and set in Toronto. The retention of the bloodmobile dialogue is one of many examples of Americanisms in the series. Obtaining money for blood donations is forbidden in Canada; yet it is explicit in the premiere, "Dark Knight" that the homeless people are paid for their blood donations. However, it should be noted that while for-profit organizations such as drug and medical research companies frequently pay for blood and plasma, this is not the practice at American Red Cross collection centers or at hospitals, which is where the vast majority of the blood in the U.S. is actually donated.