We’re still reeling from the death of Mona Vanderwaal on Pretty Little Liars (hello, nightmares), but we can’t forget about the episode’s other shocker — Spencer's arrest.

During the Season 5 summer finale (“Taking This One to the Grave”), Officer Holbrook arrests Spencer for the murder of Bethany Young. It seems like Spencer has been a suspect in the investigation of Bethany’s death from the beginning. And the cops gave Ali a lie detector test to help prove their theory. Ali told the cops that she didn’t kill Bethany Young, but not before dishing out the deets on Spencer’s drug addiction.

Ali told the cops all about her and Spencer’s final confrontation in her house the night of her “kidnapping” — and that she felt guilty for fueling Spencer’s drug habit.

Mona was able to secure the video of Ali’s interrogation, and it seemed pretty clear that the cops were trying to pin Bethany’s murder on Spencer. Their theory? Spencer killed Bethany for Ali. Since Ali was the only one who knew about Spencer’s drug problem, Spencer would do anything to keep her from telling anyone — even commit murder.

Officer Holbrook’s suspicions didn’t stop there. He even dropped by Radley to interrogate Aria, asking her is Spencer put her up to volunteering at the sanitorium.

Spencer and the Liars try to build a case against Ali by sneaking into Radley to steal audio tapes of Bethany’s therapy sessions. Ali and Bethany clearly had a history, and if they could prove it, Spencer might be off the hook. Unfortunately “A” — who might be Ali at this point — killed Mona and most likely stole the tapes.

At the end of the episode, the cops burst into The Brew and arrested Spencer for the murder of Bethany Young, and without those tapes to help prove her innocence, we’re not sure how Spencer’s going to get out of this one. Of course, we’re not even 100 percent sure Spencer didn’t kill Bethany — after all, she was caught red handed with the shovel.

What did you think of tonight’s finale? Were you shocked to see Mona die? Sound off in the comments!