The investigation into a Florida woman's murder takes a bizarre turn with an out-of-state tip about a homicidal hitchhiker. But the smoking gun comes via a local pawnshop, revealing a killer who lurks dangerously close to home.

A Pennsylvania Sunday school teacher is executed in a sniper-style attack, and the killer seems determined to throw police off the scent; then, detectives unlock the killer's timeline and solve what was nearly the perfect murder.