Task: Question Generation
Input (English):  John Buckingham (Ben Chaplin), a lonely St Albans bank clerk, orders a mail-order bride Nadia (Nicole Kidman) from Russia on the Internet. John is uncomfortable and shy, but Nadia is sexually bold. Though Nadia cannot speak English and John cannot speak Russian, they soon bond. Later on, a man she introduces as her cousin Yuri (Mathieu Kassovitz) and his friend Alexei (Vincent Cassel) turn up to celebrate her birthday. Alexei soon shows that he has a temper. After a violent altercation, Alexei holds Nadia hostage and demands a ransom from John. John has grown to care for Nadia and is forced to steal from the bank where he has worked for ten years. After the ransom is paid, he realises that he has been the victim of an elaborate con. Nadia, Yuri, and Alexei are criminals, and Alexei is actually Nadia's boyfriend.
John learns that the trio have carried out the same scam on men from Switzerland and Germany, among others. They take him prisoner, strip him down to his underpants, and tie him to a toilet in a motel. He eventually manages to free himself and quickly learns that Nadia has been left behind after Alexei discovered she was pregnant. John gets dressed and subsequently gets into a scrap with Nadia, who later reveals that she can indeed speak English and that her name is not Nadia.
John takes Nadia to turn her into the police - hoping to clear his name as a wanted bank robber. Ultimately, however, he sympathises with her and decides against it. He leaves her at the airport, where she is kidnapped by Alexei   who now wants Nadia to have the baby. John rescues her, tying Alexei to a chair. They make common cause against the two Russian men. Nadia informs John that her real name is Sophia. John, disguised as Alexei, leaves for Russia with Sophia.
Output (English): Why does Alexei leave Nadia behind?