In a small South Carolina town in 1991, 17-year-old Crystal Faye Todd, a popular high school student, was raped and murdered. With few leads, authorities asked Crystal’s male friends and acquaintances to provide a blood sample for DNA testing. Fifty-two of them agreed, including Ken Register, Crystal’s best friend. When his DNA matched semen at the crime scene, he couldn’t believe it. Neither could his mother, his girlfriend – and even Crystal’s mother. Ken had a solid alibi for the night of the murder, and he asked a question no one could answer: “If I had killed her, why would I have given blood?”