Nick Flynn, in his 20s, hasn't found his place in the world yet, but hopes to be a writer. Around the time he takes a job at a homeless shelter in Boston, his father, Jonathan, who considers himself a great writer and who hasn't see Nick in years, abruptly makes fleeting contact. A few months later, the down-and-out Jonathan shows up at Nick's shelter and becomes a resident. This disorients Nick; he doesn't handle it well, compounded by Jonathan's belligerent behavior. Nick's memories of his mother, his budding relationship with a co-worker, and his own demons make things worse. Can anything improve? Is he his father's son?

Father James is a small-town priest in Ireland whose Sunday confessionals suddenly include a threat to kill him in a week's time as a matter of principle. Deeply troubled and conflicted about how to respond, Father James tries to go on with his calling through that week. However, that proves impossible as he is confronted with a troubling variety of spiritual challenges from both his estranged daughter and his own parishioners. In those dispiriting struggles, Father James' life begins to fall apart as time runs out towards a confrontation that seems to crystallize his values and what he wants his life to be.

On a warm September evening, college professor Ethan Learner, his wife Grace, and their daughter Emma are attending a recital. Their 10-year-old son Josh is playing cello - beautifully, as usual. His younger sister looks up to him, and his parents are proud of their son. On the way home, they all stop at a gas station on Reservation Road. There, in one terrible instant, he is taken from them forever. On a warm September evening, law associate Dwight Arno and his 11-year-old son Lucas are attending a baseball game. Their favorite team, the Red Sox, is playing - and, hopefully, heading for the World Series. Dwight cherishes his time spent with Lucas. Driving his son back to his ex-wife, Lucas' mother Ruth Wheldon, Dwight heads towards his fateful encounter at Reservation Road. The accident happens so fast that Lucas is all but unaware, while Ethan - the only witness - is all too aware, as a panicked Dwight speeds away. The police are called, and an investigation begins. Haunted by the tragedy, both fathers react in unexpected ways, as do Grace and Emma. As a reckoning looms, the two fathers are forced to make the hardest choices of their lives.