The first scene of the movie introduces Fielding Pierce (Billy Crudup) as he is watching news footage showing that Sarah Williams (Jennifer Connelly) has been killed in a suspected car bombing. The reporter indicates that Sarah was an activist from Chicago involved in helping refugees from the Chilean government and that her death may cast new light on the movement. Fielding is completely distraught over hearing this news and the movie begins.
The first 3/4 of the movie unfolds on parallel timelines in the 70s and early 80s: the progression of Fielding & Sarah's complicated, volatile relationship and Fielding's ascension into power as an upcoming politician dealing with the recent loss (and haunting memories) of Sarah.
Fielding meets Sarah as he is returning, in uniform, from duty in the Coast Guard and meeting up with his brother, who is a editor. The brother, Fielding and Sarah all go to lunch where Fielding is very ouspoken in his political ideals about current events. Sarah and Fielding are both immediately intrigued by each other, Fielding's attraction being more sexual and blatant and Sarah's attraction more of curiousity and intrigue. A few dates quickly lead to a sexual relationship despite an obvious difference in political thinking between the two. Sarah asks why Fielding wants to be a senator and his very serious reply is that he doesn't- he wants to be president. Sarah is later quoted as saying "Ambition is the ice in the lake of emotion." And when Fielding tries to comfort Sarah's fear of his Coast Guard duty leading to a Vietnam tour, she replies "but if you go over there, you'll be shooting at the guys that I want to win." Their intense love outweighs their differences, though, and their relationship quickly becomes serious.
Meanwhile Fielding is a young politician being groomed to be congressman by the current govenor because of a scandal involving Jerry Carmichael 's (Ed Harris in a cameo role) resignation due to his homosexuality. Fielding seems ambivalent about the offer to be put on the ticket, perhaps because of the nature of the resignation- as he indicates- or pehaps because of the impact of Sarah's influence on his current ambitions. Either way, the governor and his top advisor Isaac (Hal Holbrook) are not comfortable with this lack of enthusiasm and do not offer much hand holding. This confrontation sets the tone for the later timeline in Fielding's life as his insecurities and haunting memories of Sarah eventually lead to hallucinations and his emotional breakdown. Fielding is now dating Isaac's daughter, but their relationship is clearly not as intense as his past relationship with Sarah. Conversations with his sister Caroline (Janet McTeer) and visits with his dad quickly lead to discussions about Sarah and how is haunting memories are leading to him seeing Sarah again. His family is supportive without offering any helpful advice other than to focus more on the political path ahead of him.
Sarah and Fielding's relationship takes them to Chicago where they share an apartment as he continues law school and she begins missionary work for a local church led by Father Steven (John Carrol Lynch). Fielding's involvement with Isaac soon begins, and Sarah's aversion to the whole political process becomes more threatening. After a uncomfortable encounter with Sarah at one of Fielding's political events, where her disdain for the situation leads to a verbal attack on one of the attendees, they attempt to reconcile on the subway afterwards. They cannot reach an agreement and she proclaims "It is so infuriating loving you!" Fielding chuckes and says that the feeling is mutual. Sarah's long hours away from home, spent working at the church, lead Fielding to foolishly suspect Sarah is having an affair with Father Steven. Their intense bond holds them together through their disagreements and insecurities.
Fielding starts the campaign trail even as his memories of Sarah convince him that she may still be alive and is watching him. He even chases someone he believes to be her through town and eventually ending at a church. But his search is fruitless and only further shows his descent into emotional breakdown. His relationship with Molly becomes troubled as he emotionally withdraws from her also. When she tries to reach to him, he does not offer any recognition of her or his feelings.
Sarah's missionary work leads to activist work in Chile where her and Father Steven bring back political refugees of the government. At one uncomfortable dinner at the church with Fielding. The refugees are appalled to hear that Fielding is hoping to enter politics, an american institution they feel is overrun with corruption. Fielding tries to convince them he is not entering politics to become corrupt but to affect change. They are not conducive to this idea. He chastises their hypocrisy by observing that as awful as they try to hint his government is, he can't help but to notice when they needed help they ran to this country for freedom. When he turns to Sarah for help, she offers "You are alone in this conversation." Fielding then replies he is alone in this whole room and he is "choking on the collective sense of superiority." Fielding and Sarah's political difference and growing distance is shown at its worst, as no make up scene follows. Soon after Sarah leaves for her fatal trip in Milwauke.