Mona, in her quest to make amends for her history of stalking and life-ruining, is in her interrogation, confessing to Wilden's murder. She says that she had known about Wilden's murder of Garrett, a fact that she claims she was trying to use to blackmail him into leaving our Pretty Little Liars out of his Ali-vestigation. Wilden got violent once he know that Mona knew about his murdering Garrett. When asked why she's confessing when she could have gotten away with it, Mona cries and says she couldn't let her best friend's mother go down for a murder she didn't commit.
Marines: As soon as the detective leaves, she stops crying and puts on a, "mwahahaha" face. I hope this isn't being recorded.