Task: Question Answering
Input (English): Passage: In 1917, France is embroiled in World War I. Dubois, head of the French spy bureau, offers to spare the life of a captured agent (an uncredited Mischa Auer) if he will reveal who he is protecting. Dubois suspects it is Mata Hari, a celebrated exotic dancer, but the prisoner chooses execution by firing squad.
Lieutenant Alexis Rosanoff of the Imperial Russian Air Force lands in Paris after a dangerous flight over enemy territory, bringing important dispatches from Russia. He persuades his superior, General Serge Shubin, to take him to see Mata Hari perform that night. Rosanoff is instantly smitten by her (as are most of the men of Paris). By youthful exuberance and good looks, he persuades her to spend the night with him. However, the next morning, she makes it clear to him that it was a one-time dalliance.
Carlotta secretly instructs Mata Hari to report to Andriani, their spymaster. Andriani orders her to find out from General Shubin the contents of the dispatches Rosanoff brought.
Meanwhile, when Dubois discloses his suspicions about Mata Hari to Shubin, the general laughs them off as ridiculous. However, Shubin has himself passed secret information to his lover Mata Hari, whom he is expecting for a private dinner. Rosanoff arrives unexpectedly, in case Shubin has further instructions before the pilot returns to Russia with more important dispatches. Upon learning of Rosanoff's mission, Mata Hari arranges for a confederate to steal the dispatches, photograph them and then return them undetected, while she keeps a puzzled, but delighted Rosanoff occupied. 
Question: Who warns the general about the exotic dancer?
Output (English): Dubois.