Task: Question Generation
Input (English):  Jack Manfred (Clive Owen) is an aspiring writer going nowhere fast. To make ends meet and against his better judgment, he takes a job as a croupier. The interview was set up by his father, a small-time hustler back home in South Africa.
Jack finds himself drawn into the casino world, and the job gradually takes over his life. He goes drinking with Matt (Paul Reynolds), a croupier whom he knows is cheating the casino. He sleeps with a fellow croupier named Bella (Kate Hardie) in contravention of casino policy. His relationship with girlfriend Marion (Gina McKee) begins to deteriorate when he lets her read part of his book about a cold, unfeeling croupier who enjoys seeing gamblers lose   a character transparently based on Jack himself. Bella confronts Jack at his apartment, accuses him of getting her fired and tells Marion about the one-night stand.
One gambler, Jani (Alex Kingston), tries to befriend Jack   another serious violation of casino rules. Jani shows him bruises saying she got them from gambling creditors and asks Jack to be the inside man for a planned robbery at the casino. All he has to do is raise the alarm when a gambler cheats at his table. Jack eventually agrees and accepts a  10,000 advance with an additional  10,000 if all goes well. In doing so, Jack notices that Jani's injuries were faked.
Marion reconciles with Jack but discovers that he is involved in something criminal and tries to foil it. On the night of the robbery, Jack raises the alarm anyway and gets beaten by the gambler as a distraction while others try to grab the money. They fail, and Jack and Marion have an argument but she stays with him.
When a late-night knock at the door comes, Jack assumes it to be the casino robbers demanding the return of their advance money. Instead, it is a policeman, who informs him that Marion has been killed in an apparent hit-and-run.
Jack finishes his book and gets it published anonymously. It is a big success, but he doesn't change anything about his life, continuing to work as a croupier and live in his basement flat, not even buying the new car he wanted.
Jack goes on with his life and gets another call, this one from Jani, who congratulates him on playing his part in the attempted robbery and implies that she benefited significantly. Then she puts his father on the phone, and he implies that he set up the croupier job for Jack in order to arrange for the attempted robbery, and he benefited as well.
Stunned but amused, Jack hangs up. Just then, Bella appears from the bedroom and kisses him.
Output (English): Why does the policeman know on Jack's door?