Sam Baldwin, a Chicago architect, has lost his wife to cancer. He and his young son Jonah move to Seattle, Washington to make a fresh start, but Sam is still disconsolate.
On Christmas evening, Jonah calls into a national radio advice show and persuades his father to go on the air with him to talk about how much he misses his wife. Thousands of women around the country, touched by Sam's story, send him letters. One letter is from Annie Reed, a journalist from Baltimore, Maryland, engaged to a nice but sneeze-prone man named Walter who feels that there is something missing. Jonah, who has been working his way through the flood of mail, finds Annie's missive and likes that it mentions the Baltimore Orioles. He tries to convince his father to go to New York City to meet her on Valentine's Day, but Sam loses his temper and refuses.
Jonah flies to New York and takes a taxi to the Empire State Building, saying he's going to meet his new mother. Sam, in pursuit, catches up with Jonah, who hasn't found Annie because she's busy breaking up with her fiancé. Jonah and Sam get on the down elevator just before a late Annie rushes in, but with the help of a lost backpack and teddy bear, they finally meet and all ends well.