Widower Sam Baldwin and his young son, Jonah, move to Seattle to start a new life. Lonely Sam is ready to start dating again, but still missing his mother, an upset Jonah calls a psychologist on a national radio talk show. Sam discovers Jonah is on the air. Sam gets on the phone and tells the psychologist that although it’s been tough, he and Jonah are doing OK. Single women across America hear Sam’s poignant story and write to him wanting to meet. East Coast reporter Annie Reed is also touched and believes Sam may be her soul mate. Even though she’s engaged to Walter, she sends Sam a letter. On the pretense of writing a story, she tracks down Sam’s address and goes to Seattle. Although she and Sam catch revealing glimpses of one another they do not meet, and Annie returns home.
Meanwhile, Jonah has read Annie’s letter, and he’s convinced she’s the one for Sam. Impersonating Sam, he writes Annie and suggests they meet atop the Empire State Building on Valentine’s Day. Sam finds out and has a talk with Jonah and thinks the matter is ended. Jonah is unfazed, however, and with the help of his playmate whose mother is a travel agent, books a flight to NYC to find Annie. A frantic Sam discovers Jonah is missing and follows him to New York.