An old man lies alone in a dark, isolated castle. He holds a small snow-globe, depicting an idyllic snow-covered cabin, as he utters his final word: "Rosebud". The snow-globe tumbles to the ground and shatters, and a nurse comes in to cover the body. This man is dead.
A newsreel reveals the details of the life of this man - Charles Foster Kane. He was the greatest newspaper tycoon who ever lived. His wealth was so immense that he built himself the most lavish home ever known, Xanadu - which is where he died. The newsreel tells the story of Kane's humble beginnings and his rise to prominence as a media mogul and controversial public figure. He eventually lost everything, and retreated from the public eye until his death.
A group of journalists watch the newsreel and feel that it lacks a personal angle. Mr. Rawlston, a newspaper editor, assigns one of his reporters, Jerry Thompson, to find out the meaning of "Rosebud". Thompson first goes to see Susan Alexander, Charles Foster Kane's second wife. She is a club-owner and drunk in Atlantic City and refuses to speak to him. He then goes to read the memoirs of Walter Parks Thatcher, who was Kane's guardian until the age of 25, which was when Kane inherited his sizable fortune. In a flashback, Thompson (and the audience) sees Charles Foster Kane as a young boy sent away by his mother so he could have a better life. He eventually becomes an arrogant and idealistic young man, not interested in any of his assets other than the New York Inquirer, a failing newspaper. He and Thatcher disagree over Kane's defiance of capitalism, leading Thatcher to eventually label Charles Foster Kane "a communist".
In his next interview, Thompson visits Mr. Bernstein, who was Charles Foster Kane's general manager and his longtime friend. Bernstein has no idea what "Rosebud" means, but tells Thompson about their early days at the Inquirer, and how Charles Foster Kane grew the paper's circulation from 26,000 to nearly 700,000 readers. In the flashback, young Charles Foster Kane publishes a Declaration of Principles, promising his readers honest journalism. Soon, though, he has embraced the tactic of yellow journalism in order to support American intervention in the Cuban war for independence. As the paper grows more influential, Charles Foster Kane marries Emily Norton, the President's niece.
Next, Thompson goes to see Jedediah Leland, who was also one of Charles Foster Kane's oldest friends. Leland's flashback reveals the dissolution of Charles and Emily's marriage, and Charles's chance meeting with Susan Alexander. During this time, Charles Foster Kane is running for Governor of New York, on the platform or reforming the corrupt practices established by incumbent Jim W. Gettys. However, Gettys uses Kane's alleged affair with Susan to blackmail him, which ends his marriage with Emily and his bid for governor in one fell swoop. The scandalous loss also marks the end of Kane's friendship with Leland, who requests a transfer to Chicago.
As a result of the scandal, Charles Foster Kane marries Susan Alexander and devotes all his energy into building her career as a grand opera singer, although she is not nearly talented enough. Leland starts writing an extremely negative review about Susan's debut performance, but falls asleep drunk on the typewriter midway through. He wakes up to find Charles Foster Kane finishing the negative review - and Kane fires Leland on the spot.
Thompson goes back to see Susan Alexander again, who picks up where Leland left off. Despite the bad reviews and Susan's hesitance, Charles Foster Kane pushes her to keep singing. After a whirlwind tour across the country, Susan can't take the disdainful audiences anymore - and tries to commit suicide. Finally, Kane allows her to stop singing. They move to Xanadu, where Susan is lonely and miserable and does jigsaw puzzles all day. Charles and Susan's marriage continues to crumble until Susan finally leaves him.
Thompson's last stop is Xanadu, where he meets with Raymond, Xanadu's caretaker and Kane's longtime butler. Raymond tells the story of what happened after Susan left Charles. He destroyed her room, but found a small snow-globe inside. Holding the snow-globe, he uttered the word "Rosebud" before disappearing into Xanadu's darkened halls, alone and miserable. This is all Jerry Thompson can find out about Rosebud, and he concludes that whatever it meant, it was only a small part of the jigsaw puzzle of Kane's life. After Thompson and his colleagues leave Xanadu, Raymond supervises the burning of some of Kane's worthless possessions. A man throws an old sled into the fire - the same sled that Charles was playing on the day Thatcher took him away from his parents - and in a close-up, a painted word on the sled is revealed as it burns: "Rosebud".