context: Dolf Vega, (Joe Flynn) a 15-year-old boy living in Rotterdam, plays a football match in the stadium of Speyer, Germany. His team loses and everybody seems to think that it is Dolf's fault. He is left utterly frustrated.Dolf's mother, Mary Vega (Emily Watson), works in a research center where a time machine has been developed. It allows an object, animal or person to be moved to a specified time in the past and a specified location. It is also possible to move to the present, and to the research center, whatever is on a specified time in the past in a specified exact location of ca. one square meter. Thus a person moving to the past can only return to the present by being at the right time on exactly the right location. The machine is being tested on animals. A special medicine is needed daily to stay alive in the past.Dolf decides to go back in time one day, and go to Germany, to replay the match. Since he regularly visits his mother at the lab and assists with the work, security guards ((David Prince, Karlijn Krijgsman and Walid Benmbarek) know him, the iris scan authorization check lets him pass, and he knows his mother's password for the computer system. This enables him to use the time machine without authorization. However, this activation of the system alarms the guards. Dolf manages to make the system work just in time before the guards can stop him, but in the hurry he accidentally enters the password in the field for the destination date, and consequently travels to the year 1212. His destination location is as planned: the location of the present-day stadium, not far from the in 1212 already existing city of Speyer.Soon after arriving in 1212 he is attacked. Jenne (Stephanie Leonidas), a girl he meets there, saves his life.He joins the Children's Crusade, a journey on foot motivated by their Christian faith, of 8,000 children from Germany to Jerusalem to non-violently conquer the city from the Muslim Ayyubid dynasty, with God's help. The leaders are the teenage boy Nicholas (Robert Timmins) and father Anselmus (Michael Culkin). They first go across the Alps to Genoa, where Nicholas expects the sea to part, so that they can walk through the sea to Palestine. However, Anselmus has a secret plan to sell the children as slaves. We see him releasing pigeons to send a message to the traders, and we see him secretly meeting representatives of them.Each time they pass a city they urge the local authorities to assist them with food and supplies, emphasizing that it would be against God's will to refuse. At Speyer, assistance is refused, after which the church of the city is destroyed by fire, caused by a lightning strike. This is interpreted as God's revenge; the responsible person who refused to assist the children is hanged, and the children are now welcome.Dolf applies his modern-day knowledge to save the lives of many children. He even saves the life of one of the leaders, prince Carolus (Jake Kedge), who almost drowns, by bringing him on shore and applying cardiopulmonary resuscitation. Dolf also helps to stop an infectious disease from spreading. He also carries modern equipment, such as his watch, his iPod, and his mobile phone (albeit without signal), and also his clothes and his Mars Bar are special for the people living in 1212. All this helps him gain respect.At Rottweil the crusaders get flour to bake as much bread as they can in one night. Dolf pays the local baker (Jack Wouterse) with his iPod for use of his bakery, and together the children bake enough bread for everyone.Dolf has doubts about the people's Christian beliefs, e.g. that the sea will part. However, the people are very aggressive against people with different beliefs; Dolf is almost executed for blasphemy.Dolf has some of the medicine with him that one needs when sent to another time, but runs out of it. Dolf's mother succeeds in sending him a new supply and a message about the time and place where he has to be to be brought back to 2006. She knows about his whereabouts from an old book describing this stranger that appeared in 1212. The book was written and illustrated by Thaddeus (Benno Fürmann), a learned monk who Dolf befriends and who will later in his life leave a recollection of the crusade for posterity. Dolf successfully returns to 2006.However, Dolf has fallen in love with Jenne and they had intended to go together, but in the confusion Jenne failed to join Dolf. Therefore Dolf wants to go to 1212 again; his mother understands, and gives him a new supply of the medicine. After Dolf leaves 2006 for the second time, the film ends, but just before the credits roll you see the modern day stadium at Speyer in which Dolf has gone back in time to replay the match and make the pass he should have made before and win the the match. That frame ends as a photo in the newspaper and the shot pans to Jenne in the same photo in modern day clothes watching the match.
question: Who does Dolf persuade to let him go back to 1212?
answer: Dolf's mother.