12. Taking This One to the Grave

The police are hellbent on finding a connection between the liars and Bethany Young. Alison agrees to take a polygraph test, leaving the other girls to wonder what her story is going to be this time. They know just who to ask for help: Mona Vanderwaal. Mona concedes that her anger toward Alison has been unfairly directed at the other girls, and she apologizes. She agrees to find out exactly what Alison is telling the police. Mona hacks into the police computer system and downloads a video of Alison’s interview.

The polygrapher’s questions assume a scenario where Spencer killed Bethany to gain favor with Alison. Caleb discovers that Spencer has replaced Alison as the prime suspect in Bethany’s murder. This change was made just after the police uncovered information related to Bethany’s time at Radley. The group hatches a plan to get Bethany’s Radley files. Hanna and Caleb hack the building’s security system while Spencer and Mona sneak inside. Aria causes a distraction in the art room so Mona can snag a set of keys.

Meanwhile, Emily keeps Alison busy and away from their heist. They end up finding and stealing audio recordings of Bethany’s counseling sessions. The following day, the girls are at The Brew when Detective Holbrook bursts through the door. He arrests Spencer for the murder of Bethany Young. Mona goes through the recordings of Bethany. She learns that Bethany knew about an affair between her father and Alison’s mother. Mrs. DiLaurentis was bribing her to keep it quiet. Mona concludes that a jealous Alison lured Bethany to Rosewood the night she died.

She calls Aria to relay this information. Meanwhile, a figure with blonde hair and a black hoodie sneaks inside Mona’s house. Mona is just getting off the phone when the figure opens the door to her bedroom. Mona is shocked, scared, and cornered. Aria brings Hanna and Emily to Mona’s house where they find a disturbing scene. There are clear signs of a struggle inside, and blood is splattered everywhere. The police survey the area and determine that Mona Vanderwaal has been murdered. ' A' ending: ‘A’ replaces the baby Jesus in Emily’s nativity scene with a Mona doll. They open the trunk of a car to reveal Mona’s lifeless body. In a separate scene, ‘A’ makes a snow globe and puts photos of the liars inside.