90年代末，一个男孩和他的父亲踏上了前往城市的绿皮火车，男孩喜欢听音乐，喜欢独自享受自己的音乐时光，但是现实总是不遂人意，男孩的父亲并不理解。 在火车上，男孩遇到了一个女孩，女孩的母亲喋喋不休的教育着女孩为什么输掉了钢琴比赛，断送了前往音乐学院的路，女孩啜泣着，男孩看在眼里。男孩的父亲发现了男孩自制的纸质琴键，教训男孩，为什么不珍惜机会，专心学习，男孩无声，只能听着，任凭父亲打压着自己小小的梦想。男孩和女孩是同病相怜。夜晚，男孩听着磁带，失望中带着痛苦，在卧铺的墙壁上轻轻敲击着钢琴的旋律，然而，对面的床铺竟然也出现了敲击的声音，并且和男孩弹奏的是同一支曲子！ 男孩紧张的又轻轻敲击了一段旋律，对面出现了回应，一墙之隔，男孩和女孩完成了一首合奏。在幻想的世界中，他们相遇了，手指在琴键上跳舞，群众组成的交响乐队为他们伴奏，他们想象着自由，一曲过后，他们窃窃私语，互相道别。白天，男孩惊醒，想要看一眼对面却发现已经没有人了，男孩看向窗外，望见了女孩的背影，完成了最后一次合奏，并各自踏上了未来的旅程。 In the 1990s, a boy and his father took on a green train to a city. The boy loved music and enjoyed listening to music by himself. However, the reality was not what he expected. His father didn’t understand him. The boy met a girl on the train. Her mother was ceaselessly questioning her the reason of losing the piano contest, thus ruining the precious opportunity of entering the Music Academy. The girl was sobbing, and boy saw this scene by accident. Boy’s father discovered the paper-made keys which were fabricated by the boy himself and scorned him. The elder one asked him why he didn’t cherish the opportunity to focus on his study. The boy remained silent and let his father crush his little dream. The boy and the girl suffered the same hardships and shared the same sympathy. When the night fell, the boy listened to the tape, felling disappointed and painful. He thus softly tapping the melody of the piano on the wall of sleeping berth. Surprisingly, the person on the opposite sleeping berth tapped back the tune of the same song. Being nervous, the boy tapped another piece of melody and the opposite one tapped back again. With a wall standing between them, they completed an ensemble. In a world of imagination and fantasy, they met with each other. Their fingers were dancing on the keys and a symphony orchestra which was made of crowds accompanied them. They dreamed of freedom. After completing the performance, they whispered to each other and bid farewell. The boy woke up suddenly the next morning and wanted to see the person on the opposite. However, there was no one there. The boy glanced through the window and saw the shadow of that girl. They completed the final ensemble and embarked on their own path towards the future.