Dr. Aziz comes to join Duncan in his research but Duncan finds it hard to understand him. Aziz leaves but a preparation of his is given to McCorquedale, a racist, bigoted Scots patient, as a sedative. Once again Duncan finds it hard to read Aziz's instructions and the wrong dosage is given - turning the patient black. Aziz makes it clear he left, not because he felt he was bullied racially but he found the staff incompetent and impossible to work with. (thetvdb.com)