Doctor Kadan was a Quarren Neuropsychiatrist at the Central Hospital, in the capital city of Quarra. In the 2370s, he used drugs to control people who were kidnapped and used for the Quarren workforce. He made false diagnoses on people, altered their memories so he could solve the work shortage on his planet. Almost all of the USS Voyager crew was subject to this treatment. After a police officer named Yerid was convinced by Chakotay of the plot, he helped free the Voyager crew and arrested Kadan, exposing the conspiracy to the authorities. (VOY: "Workforce", "Workforce, Part II")