Amber Tuccaro was 20 years old when she left her infant son with a friend at a motel on the outskirts of Edmonton, and got into a vehicle with an unknown man. She was never seen alive again. But Amber left an important clue: A chilling recording of what appear to be the final moments of her life, and the voice of the man who may be her killer. Days after police released that recording to the public, Amber’s remains were found in a field outside the city. She would be one of five women whose bodies were discovered in that area, and one of dozens more found in rural areas around Edmonton,...