Confessions on the 7:45 is based on Lisa Unger's book of the same name, which focuses on Selena Murphy, a working mom who strikes up a conversation with a stranger while they are stuck on a train. As the two converse, the woman begins telling Selena about an affair that she's having. Once the two part ways, however, mysteries begin popping up in Selena's life, leading her down a path that might cause her to meet with the mysterious stranger again.