Dark Echo tells a story in which Dexter is challenged by a copy-cat killer who does not follow any sort of code. Dark Echo opens immediately after the death of Dexter's father, Harry, with Dexter in his early twenties and his sister Debra still in high school. Dexter is enrolled in medical school where he's studying anatomy to improve his "craft." During a routine kill, Dexter realizes that another student has been spying on him and knows that he is a serial killer. He confronts the student after he begins to commit murders in Dexter's style and the two clash over the ethics of their situations.