Susan and Kane fall in love with each other under false pretenses, and though Susan eventually loses her illusions about the kind of man Kane is, Kane is never able to see Susan clearly. Susan and Kane first meet in the street: Susan has a toothache, and a passing car has splashed Kane with mud. Circumstances have diminished the social, age, and class differences between the two that may otherwise have thwarted their connection. Susan, usually screechy and overbearing, here seems soft-spoken, gentle, and naïve because of her toothache, and Kane’s helpless predicament makes her laugh. She has no idea who Kane is. Kane, charmed by her unselfconsciousness, believes he has found someone who will love him unconditionally. When Susan’s true nature emerges, Kane willfully ignores it. She grows bitter when he pressures her to become someone he believes is more suited to his station. Kane tries to force others to see her as he does, which nearly drives her to suicide. Kane’s attempts to completely control her almost rob her of her identity, and the only way she can save herself is to leave him.
Susan's appearance in Kane's life is the fulcrum on which Kane's fortunes turn. Kane’s life before meeting Susan is very different from his life after meeting her, and Susan effectively splits the movie into two parts: the world of Kane’s rise and the world of his fall. Before Kane meets Susan, his story plays out in a world where he’s ruthless, successful, and respected. After meeting Susan, his story becomes inseparable from their relationship and their life together. Because of his relationship with her, his marriage breaks up, his political aspirations shatter, and he loses the respect of society at large. Susan represents Kane’s lost innocence and fall from grace. When Susan finally leaves him, the loss Kane feels mirrors the loss he felt when his mother left. He trashes Susan’s room and finds the snow globe, which brings back long-repressed memories of his childhood. Kane has no one now that Susan is gone, and nothing to hold onto but the past.