The tranquility of the library is shattered by a woman's terrified scream. Security guards take charge immediately, instructing everyone inside to stay put until the threat is identified and contained. While they wait for the all-clear, four strangers, who'd happened to sit at the same table, pass the time in conversation and friendships are struck. Each has his or her own reasons for being in the reading room that morning―it just happens that one is a murderer.

After witnessing her teenage son kill a man, a mother falls asleep in despair, wakes up and it is yesterday, and wakes up again and it is the day before yesterday, getting chance after chance to stop the murder and save her son.