Derek finally remembers his past life in which he killed Alex's past incarnation. It was 1865, the year the American Civil War ended. His past self was not a bad person, nor Alex's past self (a man). Nancy, who was also incarnated as a man, could not prevent it with all his intelligence and dedication to Alex.
This is the last Book (installment) of I Remember You series. Can Derek forgive himself? And how does this remembering influence his current relationship with Alex? And can Nancy make peace with herself and overcome her fear of success?