If there is any case where you wish you could turn back the clock and change just one small decision, it might be the disappearance of Bianca Lebron. There were several moments that morning in November 2001 when a question, a phone call, or one person stopping her before she walked away might have changed everything that came next.

One night in October 2006, a college student needed to borrow a phone. She happened to ask a stranger with violent intentions. What makes that even harder to sit with is what investigators learned about this man afterward. There were red flags everywhere, allegations that reached back years, but none of it stopped him from being there that night.

On a Saturday morning in 1990, the body of a teenager was found on a dead-end street in the Dorchester neighborhood of Boston, Massachusetts. The scene raised immediate concerns, but the autopsy did not answer the question everyone needed answered most: how did Kasha Blount die?