The Good Daughter Ending Explained: Who Was Zach Culpepper's Accomplice? And Who Orchestrated The School Shooting?

The sixth and final episode of The Good Daughter revealed several key details about the events at the Quinn farmhouse and the school shooting. Zach Culpepper, played by Jake McDorman, admitted he was the second masked assailant who accompanied his friend, Charlie (Meghann Fahy), to the farmhouse years prior. Zach also confessed to setting fire to their home and murdering their father, Rusty (Brendan Gleeson), as well as their mother, Gamma (Olivia Williams), and Charlie.

However, Zach's accomplice in the school shooting was Kelly Wilson, portrayed by Shayna Benardo. Security footage suggested she had loaded the gun used during the attack that killed Principal Douglas Pink (Kovar McClure) and another student, Emma (Emma Bell). Kelly confessed to pulling the trigger, though the security footage did not conclusively show her doing so. Instead, it revealed two different hands on the gun, leading the family to suspect Judith Pink (Paula Malcomson) might have been responsible.

Judith had orchestrated the school shooting in an attempt to kill her husband, Douglas (Kovar McClure), who was having an affair with Kelly. She manipulated Kelly into believing Douglas wanted to force her to have an abortion, convincing her to bring her father's gun to school. Unfortunately, Kelly froze during the moment, and the gun discharged, killing Emma accidentally.

Judith then shot Kelly in the head, intending to emerge as a grieving widow and hero, collect her husband's life insurance money, and escape prosecution for her crimes.

In the end, the Quinn sisters decided to turn Zach Culpepper in to the authorities, while Kelly accepted a reduced sentence of five years in prison. Sam (Rose Byrne) and Charlie (Meghann Fahy) hoped for a happier future together, with Charlie moving to Atlanta to start a new life.