The Other Man tells the story of Peter (Liam Neeson) who discovers that his wife Lisa (Laura Linney) has been receiving emails and mobile messages from Ralph (Antonio Banderas), a man he never knew existed. Peter’s obsession with this unknown rival escalates and, against the advice of his daughter Abigail (Romola Garai), a hurt and vengeful Peter flies to Milan to seek out the mysterious Ralph and the truth about his relationship with Lisa.