Double Cross - S1.E12

Henry and Alec visit Anne Knight, daughter of Henry's old friend, who now runs the Imperial Stables. One of her horses is running against the Black in an upcoming race and her trainer wants to make sure that their horse wins. The Black's sweet tooth creates an opportunity for sabotauge and when he wins, he's disqualified due to being drugged. Henry and Alec frantically try to figure out who drugged the Black and how. They discover that he was drugged with chocolate and Henry deduces that Greg Hill, Anne's top trainer, used the candy just as his father did long ago. Anne fires Greg and apologizes to Henry.