At the beginning of the day, New York taxi driver Ed Nielson greets his mother in his usual crabby mood, complaining that he has to make a payment on his cab today. Mrs. Nielson, who believes that marriage will help her grouchy son, informs him that their neighbor, Mrs. Albert, and her daughter Florence are coming for dinner that night. Ed growls that he is happy without a wife. On his first fare, Ed tries to take a longer route than needed, but the passenger informs Ed that he used to live in New York and gives Ed only a nickel tip. He then loses two fares at the Brooklyn docks, but a policeman informs him that a passenger freighter is unloading. At the U.S. Immigration Office on the dock, Mary Turner, arriving from Dublin, is given a landing card and an advance of five dollars on wages she has earned washing dishes on the trip over, then is told she must be back by five o'clock. Ed takes her on a roundabout route through Coney Island and New Jersey before arriving at the Manhattan address she has given him, which turns out to be an empty lot. Mary is trying to find her husband Jim, a traveling writer she met in Ireland a year ago and married after knowing him only a week. When Ed learns that she has only $5 to pay the $12.20 bill, he explodes, but then agrees to help find her husband so that he can get his money. After speaking with an Italian delicatessen owner, they find the wife of the janitor who used to work at the demolished building, an African-American woman who gives Mary a box of Jim's clothes and letters Mary had written that never reached him. Her only lead as to Jim's whereabouts is a pawn ticket. The pawnbroker on Park Row finds an overcoat that Mary excitedly remembers as Jim's. She is further encouraged when she sees a statue of St. Anthony and buys it for $1, as the saint is known to help find things that are lost. Just then, the pawnbroker notices a coatroom stub fall from the pocket of the overcoat. The stub is from Billy's Grill, a hangout for reporters. As they return to the taxi, they find a policeman writing a parking ticket. Noticing that the policeman looks Irish, Mary talks to him about the town his ancestors came from and, using "a bit of the blarney," succeeds in getting him to stop writing the ticket. At Billy's, Mary learns the name of Jim's publisher, Leggett & Millard. In the publisher's office, Miss Millard informs Mary that Jim went West to finish a novel and suggests she return to Ireland, causing Mary to cry. When Ed's taxi does not start, he takes the St. Anthony statue out to get his tools, then unknowingly leaves the statue on the curb after getting the car to run. At the pier, Mary thanks Ed and tells him that the ship's captain will give him his money. Ed is about to pick up another fare, but as he opens the trunk, he sees Mary's box of letters and runs after her. On the ship, he finds her with her infant son Kevin. She relates that she came to America to find Jim so that the baby would not wind up in an orphan asylum. Impressed with her dedication, Ed tries to bribe an immigration official to let Mary stay until her husband arrives. Insulted, the official says Ed must come up with a $500 bond to insure that she appears at an immigration hearing and suggests that he use his cab as collatoral to obtain a loan. Despite the pain this creates, Ed arranges for the loan, then brings Mary and the baby to his apartment. They arrive as Mrs. Nielson is visiting with the Alberts, who leave in outrage when Ed says he has brought Mary and Kevin there to live. While Mrs. Nielson questions her son, Mary sneaks out with the baby. Ed finds the baby in a Catholic Church, and thinking Mary has jumped into the East River, he is about to break down in tears, when he hears her praying to St. Anthony for help in finding Jim. Ed brings Mary home, where Mrs. Nielson takes a liking to her, as she herself had a broken first marriage. Mary sees a news story on television about the St. Anthony statue, which has been found across from St. Patrick's Cathedral. As the reporter interviews bystanders, Mary recognizes Jim, who gives his address. Ed drives her there and waits below with the baby. Mary learns that the apartment belongs to Miss Millard, who admits she was once married to Jim herself. This upsets Mary, as she would not have married him if she had known because of her Catholic beliefs. Miss Millard reveals that Jim is now broke and has asked her to marry him again. She says she does not want him now, and sends Mary to see him in another room. When she returns to the cab, Mary tells Ed that Jim was happy to see her. Taking Kevin, she kisses Ed on the cheek and blesses him. She goes into the building, but after Ed drives off, she comes back out. He pulls in front of her and tells her to get in, saying he could not believe her phony story, and Mary realizes she has never seen him so happy.