Task: Question Answering
Input (English): Passage: Englishman Rudolf Rassendyll decides to pass the time by attending the coronation of his distant relation, King Rudolf V of Ruritania (also played by Stone) . He encounters an acquaintance on the train there, Antoinette de Mauban, the mistress of the king's treacherous brother, Grand Duke 'Black' Michael.
The day before the coronation, Rassendyll is seen by Colonel Sapt and Captain Fritz von Tarlenheim. Astounded by the uncanny resemblance between Rassendyll and their liege, they take him to meet Rudolf at a hunting lodge. The king is delighted with his double and invites him to dinner. During the meal, a servant brings in a fine bottle of wine, a present from Michael delivered by his henchman, Rupert of Hentzau. After Rudolf tastes it, he finds it so irresistible that he drinks the entire bottle by himself.
The next morning, Sapt is unable to rouse him; the wine was drugged. Sapt is afraid that if the coronation is postponed, Michael will seize the throne. The country is dangerously divided between the supporters of Rudolf and of Michael. The colonel declares that it is Fate that brought Rassendyll to Ruritania; he can take Rudolf's place with no one the wiser. The Englishman is less certain, but he tosses a coin, which lands in Rudolf's favor, and Rassendyll goes through with the ceremony. Afterwards, he is driven to the palace in the company of the universally adored Princess Flavia.
Later, when Rassendyll returns to the lodge to switch places with the king once more, he and Sapt find only the corpse of Josef, the servant left to guard the king. Rassendyll is forced to continue the masquerade. 
Question: What is the alias of the person that Sapt is afraid will steal the throne?
Output (English): Black.