Pretty Little Liars Melissa's dark secret was revealed in "Pretty Little Liars" Season 5 episode 11. Photo: ABC Family

“Pretty Little Liars” fans have been hit with dozens of mysteries since the show first premiered, however one major one was solved in Season 5 episode 11. Viewers will remember that Melissa whispered something in her dad’s ear while at the police station during the Season 4 finale -- and what she told him was finally revealed during the Aug. 19 episode, “No One Here Can Understand Me.”

Spencer was at her house with Hanna when she discovered a letter underneath her bedroom door. The letter was a goodbye note from Melissa, explaining that her dad had taken her to the airport and that answers would come soon.

And Melissa wasn’t lying -- later in the episode Toby discovered another envelope at Spencer’s house. The envelope was marked “private” and “confidential” and was sent from the Philadelphia airport before Melissa left. Inside the envelope was a DVD … with a confession from Melisssa.

“Spencer, you’re right. I have to tell you the truth before it's too late,” Melissa told her sister in the video. The recording explained that she was going back to England, and that their dad wanted her to leave town ever since she told him what she knew that night at the police station. However, she explained to Spencer that she couldn’t leave her again … “not like this.”

“I’m going to tell you the truth and you can do whatever you want with it,” Melissa continued. “Maybe it’ll help you, maybe it won’t. But at least you know.”

Melissa revealed that she saw Spencer the night that Alison disappeared. Spencer had been fighting with Alison and had a shovel in her hand. Shortly after Melissa discovered “the body” on the ground. Because the body was wearing Alison’s infamous yellow top, Melissa immediately believed that Spencer had snapped and killed Alison with the shovel. However, she acknowledged in the video that she’s not sure what happened to the girl. She never saw the face, but fearing that Spencer was involved with the death, she pushed the body into a hole in the ground and buried it. It wasn’t until recently that she realized that it wasn’t Alison she had buried -- it was a stranger who Melissa accidentally buried alive in an effort to protect Spencer.

That stranger turned out to be Bethany Young, the mysterious teen from Radley who had a bizarre connection to Jessica DiLaurentis.

What did you think about Melissa’s big reveal in episode 11 of “Pretty Little Liars”? Tweet your thoughts to @AmandaTVScoop.