After the end of World War II, Peter Kuban, a Hungarian displaced person and survivor of the Nazi concentration camps, stows away in Trieste on a ship bound for New York City. However, he is spotted by ship officials and held for the authorities. When the ship arrives in New York City, he claims that he qualifies for entry under an exception for those who helped Allied soldiers during the war, but all he knows about the paratrooper he hid from the enemy is that his name is Tom and he plays clarinet in a jazz band in New York City's Times Square. The immigration authorities, led by Inspector Bailey, say that without better documentation he must be sent back to communist Hungary on the ship, which departs the next morning. He jumps off the ship, breaking some ribs, and starts searching for Tom. He encounters an unemployed ex-factory worker named Maggie Summers. When she steals a coat in a restaurant, Peter helps her elude the police. They go to her apartment, where she tends his injury as best she can and learns his story. When her landlady, Mrs. Hinckley, threatens to evict her for being behind on her rent, Peter gives her all the money he has. Eddie Hinckley, the landlady's son, barges in and tries to get amorous with Maggie. Peter bursts out of hiding and starts fighting him, but gets the worst of it. Maggie knocks Eddie out with a chair and flees with Peter. The Hinckleys notify the police. Meanwhile, Tom sees Peter's picture on the front page of a newspaper. He wants to go to the immigration department, but his girlfriend Nancy persuades him to attend an important audition instead. Tom impresses band leaderJack Teagarden, but leaves abruptly to try to help Peter. The fugitives are recognized in the subway. The police grab Maggie, but Peter gets away. She meets up with Tom. After hearing Tom's story, Inspector Bailey believes that Peter can stay, but only if they can reach him before 7 am when the ship he arrived on will depart and, by law, Peter must be jailed and deported. The trio drive around searching. Peter slips into an unoccupied taxi and falls asleep. When burlesque dancer Tanya gets into the taxi after work, she recognizes Peter from the newspaper photo. She takes him to her apartment for rest and a meal. When he asks why, she explains that her real name is Bella Zakoyla, and that she is a fellow "Hunky". Her immigrant mother approves, but her brother Freddie does not want to risk getting into trouble, saying that it is the responsibility of the United Nations. The loud argument rouses Peter, sleeping in the other room, and he slips away. Acting on Freddie's remark, Peter heads toward the United Nations building in the early morning hours. He is recognized on the way and the police are alerted. Peter delivers a soliloquy to an empty meeting room with places marked for representatives of the U.N.'s member states. He calls for recognition that peace and freedom for the world require peace and freedom for every individual. The police, Maggie, Tom, and Bailey pursue Peter through the halls of the U.N. Peter panics and flees to the roof, where he contemplates jumping. Maggie and Tom reach him and at the sound of Tom's voice Peter collapses onto the roof. All reassure Peter that he is now safe.
In 2011, film critic Dennis Schwartz wrote, "Columbia's off-beat postwar noir project, whose title is taken from the U.N.'s glass wall, turned out rather well despite a number of awkward moments as it promotes its leftist agenda." The Glass Wall shared the Golden Leopard, the top prize of the Locarno International Film Festival in 1953 with Julius Caesar and The Composer Glinka.
