The summer finale for “Pretty Little Liars” aired on ABC Family on Tuesday – forcing fans to say a permanent goodbye to one major character.

With Alison gone rogue, the Liars feared their former friend would turn them in to the police. That left only one option – turning to Mona for help. The girls and Caleb hacked into the police database to see what Alison told them. And even though she didn’t actually sell anyone out, the police asked suspicious enough questions for the Liars to realize that they have a big problem on their hands. An affidavit sent out by Detective Holbrook revealed that they believed Alison was innocent in the murder of Bethany Young … but that Spencer wasn’t.

In order to clear Spencer’s name, the group hatched a plan to break into Radley and get Bethany Young’s files. Spencer and Mona broke into the institution under the disguise of nurses while Caleb and Hanna eased them through security using the computer software. Meanwhile, Aria worked from the inside while distracting a nurse during her volunteer shift, and Emily lured Alison to her house to keep her in clear sight.

Unfortunately, their plan quickly fell apart. Spencer and Mona succeeded in finding the files – which revealed that Mrs. DiLaurentis had been having an affair with Bethany’s father and that Bethany knew Alison. But then Holbrook showed up at Radley to question Aria about Spencer. Holbrook didn’t catch the girls, but Alison caught on that she was set up. She left Emily’s house in a huff, jumping in a car with Cindy and Mindy.

Spencer and Mona escaped Radley with the files, but on the way out Spencer was on the phone with Toby and listened as he got into a bad car accident. But don’t fret – Toby turned out to be fine except for a broken leg.

The following day was Thanksgiving, and Paige revealed to the girls that she had followed Alison, Mindy and Cindy from Emily’s house. Alison went to an abandoned car that had at least a dozen cars outside. The girls quickly realized that Alison was building an army of her own.

They didn’t have time to dwell on the new information because Holbrook busted into the Brew to arrest Spencer for the murder of Bethany Young. The girls alerted Mona, who was hard at work going through Bethany’s Radley files.

After her mother left the house, Mona discovered that Alison had knew about the affair and had lured Bethany to Rosewood because she was jealous and wanted her dead. Mona immediately called Aria to tell her, but what Mona didn’t know was that she was being watched. Aria immediately hung up the phone, alerted the others, and headed to Mona’s house with Ezra. But when the group got there it was too late – a blonde girl wearing a black hoodie and leather gloves broke into Mona’s house and murdered her.

Walking inside, the group discovered that Mona’s house was completely destroyed, with blood smeared everywhere. Someone let a blood-curdling scream out when they got upstairs, but a police report later revealed to the “Pretty Little Liars” audience that no body was at the scene.

“The investigation is ongoing,” Holbrook told reporters. “But we have ruled this a homicide.”

He explained that no body was found, but the amount of blood suggests that the wounds were fatal.

“Mona Vanderwaal was murdered,” he confirmed.

The “Pretty Little Liars” summer finale concluded with “A” replacing the baby Jesus in Emily’s Nativity scene with a Mona doll. “A” then proceeded to put the baby Jesus in the trunk of her car … on top of Mona’s dead body.