Thrill Kill and Poisoned

S2, E4: When a young girl disappears in Jefferson City, Missouri, police suspect the victim's family due to their criminal past. But the investigation takes a darker turn when the real perpetrator turns out to be a 15-year-old thrill killer. A teenager poisons her own grandmother with no apparent cause. Some suspect that it was due to a history of abuse, but others believe her motives go much deeper, all the way back to the mother she never knew.