On the eve of Armistice Day, itinerant jack-of-all-trades Ernest Verdun Mott visits the tomb of the unknown warriors who died in World War I and remembers his father, one of the soldiers killed during the war. After leaving the tomb, Ernie wanders the darkened street of London's poor East End where he grew up. When he enters his mother's second-hand store, Ma Mott bitterly asks why he has returned after such a prolonged absence and tells him that he must stay home now or leave forever. Angered by his mother's ultimatum, Ernie declares that he will leave in the morning. In the street outside the shop, Ernie sees their neighbor, Aggie Hunter, who is in love with him. Aggie plays her cello for Ernie, but when she suggests that they meet later that night, he balks at making any commitments. Instead of visiting Aggie, Ernie goes to the arcade, where he meets gangster Jim Mordinoy, who offers him some money. After rejecting Mordinoy's offer, Ernie sees the waif-like Ada taking tickets at a booth, and is immediately smitten. Ernie makes a date with Ada, but when, at the end of the evening, he tells her that he is leaving the next day, she denounces him for toying with her feelings. The next morning, Ma confides in her friend, pawnbroker Ike Weber, that she is dying of cancer. At breakfast, Ma and Ernie quarrel again, causing Ernie to storm out of the house. Outside Ernie runs into Aggie, who offers to support him on condition he marry her. Rather than respond to Aggie's offer, Ernie goes to Tate's fish and chip parlor, where he meets Ike. Realizing that Ma needs her son to care for her, Ike tells Ernie of his mother's condition. That night, Ernie is befriended by peddler Henry Twite, and after spending an evening at the bar, the two drunkenly wander the streets as Ernie calls out to his dead father. Upon returning home, Ernie tells his mother that he has decided to stay and they make peace. Five weeks later, Ma winces in pain while eating dinner and sends Ernie out of the house. Ernie then decides to visit Ada, who informs him that Mordinoy has forbidden her to see him. Undaunted, Ernie makes another date with Ada for later that week. On his way home, Ernie meets Aggie, and when he asks her advice about Ada, Aggie tells him that she still loves him. The next day, Ma is visited by Mrs. Snowden, a shoplifter, who tries to convince her to fence stolen goods. Ma resists the offer until Mrs. Snowden makes her feel guilty about not providing her son with a decent inheritance. The night of their date, Ada asks Ernie to take her dancing at Mordinoy's club, where the gangster offers him a job and informs him that Ada is his wife. Although Ada protests that she is divorced from Mordinoy, a stunned Ernie refuses to believe her. The next morning, while working at the shop, Ernie becomes overwhelmed by the abject poverty surrounding him when an old lady is forced to pawn her pet bird and the bird dies. When her son cries out for a decent human life, Ma decides to visit Mrs. Snowden and agrees to be her fence. The incident also causes Ernie to accept Mordinoy's proposition, but when he informs Ada, she shows him her baby daughter Kitty and warns him that his association with Mordinoy will lead to jail. Ignoring Ada's warning, Ernie goes to work stealing cars for the gangster. Alarmed, Ada begs Ernie to run away with her, but he refuses to leave his dying mother. Later, Ernie incurs Mordinoy's wrath when he stops one of his men from beating Ike while the rest of the gang ransacks the pawnshop. That night, Twite warns Ernie that Mordinoy's men are looking for him, and the two, accompanied by the Motts's dog Nipper, go to the arcade, where they meet Mordinoy and Ada. Although the gangster orders him to stop seeing Ada, Ernie insists that they be married in the morning. Ernie then entrusts Ada with Twite and Nipper as he goes to finish his conversation with Mordinoy. After buying a rifle from the arcade, Ernie accepts a ride with Taz and his brother, two of Mordinoy's men. When the police recognize their car as stolen, they begin a pursuit, and in their flight, Taz's brother collides with a truck and the car explodes into flames. Rescued from the crash, Taz and Ernie are taken to the police station. After the police find Ernie's platinum cigarette case, a birthday gift from Ma, they question him about it. Ernie refuses to answer, so the police send for Ike, whose address they found on a postcard that Ernie was carrying. After identifying Ernie, Ike bails him out of jail and he returns home. At Ma's store, Ernie finds Twite and Aggie waiting for him and learns that this mother has been arrested because the cigarette case was stolen. Ernie rushes to the prison hospital, where his dying mother advises him to find a wife to look after him and begs his forgiveness for disgracing the family. Later that night at the bar, Ernie plays Twite the music box that he plans to present to Ada's daughter at their wedding the next morning. To the strains of the music, Twite reads Ernie a note from Ada, informing him that she has decided to return to Mordinoy. As the two walk along a bridge, Eddie asks, "When will the world awake from this midnight, when will humanity get up from its knees?" When they hear the roar of bomber planes flying overhead, Twite replies that war may make a better world. Vowing to fight for a "human way of life," Ernie returns to his street and hears Aggie playing the cello. After stopping to peek in her window, he disappears into her doorway.