Secrets revealed

This is still in episode 21 (one episode before Season Finale) The betrayal begins…

Police station, Sheriff Forbes' office

Mason Lockwood is sitting on top of the table while Liz Forbes pours him a drink. They were discussing the vampire problems in the town when Elena walks in.

“Elena!” The sheriff says. She puts the drink down and turns to Elena who looks quite upset. “Is everything alright?”
“Oh, I’m sorry, Mrs Forbes, I didn’t want to bother you… I can come back later.”she says as she sees Mason, who is perched on the edge of the table.
“No, no, it’s okay, honey. You’re not bothering at all. Take a seat.”
Elena sits down on the chair in front of the table and the sheriff sits next to her in an armchair. Elena is very nervous and doesn’t know how to start…
“There’s something you need to know… I know I should’ve come earlier, I wasted time, but… it was really hard for me. And I don’t know what to do! More people could be killed and I can’t handle that.” She takes a deep breath and continues: “It’s about Katherine. She’s not my sister. She’s a vampire.”
“What? What do you mean? Did someone turn her?” The sheriff is confused.
“No, no. She’s not my sister. She’s my ancestor, it’s complicated.  But she’s been killing all these people and you have to do something to protect others…”
“Oh, my God…” Liz is very shocked now. Mason doesn’t say a word, he’s just observing.
“She won’t stop. She loves messing with people, she’s doesn’t have a… soul!” Elena goes on. “And I don’t know what you can do against her, but… I thought you should know this.”
The sheriff looks at Mason, who is really tense.
“I can’t believe this!” Liz says. She turns back to Elena: “Why? Why is she doing this? And why does she look like you?”
“I don’t know how to explain it, I’m related to her somehow, that’s all I know.” Elena is so nervous she gets up and walks around in the room. “She’s been torturing me all these months.” She’s talking more to herself now than to the sheriff. “I don’t know why she’s here, but… I want her gone. I want her gone more than anything. She thinks that only because she turned them she has the right to do anything!”
“Turned them? Who? Who did she turn?” The sheriff asks.
Elena stops. She couldn’t believe she spilled that out. What is she going to do now?
Liz Forbes gets up and walks to her and holds her hand. “Elena, tell me. Who did she turn?”
Elena doesn’t know what to say. She can’t even look at the sheriff. After a few moments of silence Mason says it:
“Damon and Stefan Salvatore. Long time ago.”
The sheriff turns to him, her face is so white, she seems like she’s about to faint. She sits down. She can’t find the words, but Mason does it for her.
“They’ve been fooling you since they moved back last year.”
“Damon and Stefan…? Is this true?” she asks Elena, who nods. “What… you knew this? You knew it all this time and never said anything!?”
“Liz…”Mason tries to calm her down.
“How could you!?” She gets up angrily. She walks around, trying to calm down. The she asks: “Wait.. how do they walk in the sunlight?” No answer again. She repeats her question: “How do they walk in the sunlight, Elena?” As she doesn’t answer Mason does it again:
“They have magic rings that protect them from burning.”
“Magic rings…? You mean…”
“Yes, there are vampires… and witches.”
“And werewolves.” Elena adds, irritated. Mason gets up from the table and gives her a warning look. She look back at him and continues: “They should all be killed too, they’re too aggressive.”
“What?” the sheriff is devastated by all this. “What do you mean…”
Elena looks at her and interrupts her. “I have to go. But I’m sure Mr Lockwood can answer all of your questions.” She gives him a hostile look then storms out. She’s really pissed at him, she didn’t want to betray Stefan and Damon. But now it’s done… And she doesn’t know what’s next.

After Elena left the sheriff’s office, Liz Forbes attacks Mason.
“How could you do this? How could you hide this… how could you lie to me all this time!? I trusted you! I thought you were helping us!”
“I am helping you! But you don’t understand…”
“What? What do I not understand? That you’ve been fooling me? That you let Damon Salvatore fool me and the whole council? What the hell were you thinking!?” she yells at him.
“I know you are mad at me, but there’s a reason for all of this…”
“No there’s not. There’s no acceptable reason for what you’ve done. They killed all those innocent people, children.. and who knows who else! And the werewolves!? I never heard of them! What is this madness?”
“I don’t know, I don’t know anything about werewolves. And they didn’t do it…”
“What are you talking about? Damon and Stefan and that… Katherine did all this and you knew it!”
“No, Liz, they did not! Listen to me…” he holds her shoulders and looks into her eyes” It wasn’t any of them. I know who killed those people. And there’s nothing you can do about it.”
“Who did it then? Tell me, Mason!”
“I can’t do that.” He turns away from her. He can’t tell anyone.
“Why not?”
He doesn’t answer.
“Well, you’re not giving me a lot of options. Guess I’ll have to take it from here.  We’re gonna attack them tomorrow. We have vervain and…”
“What? No, no, no, you can’t do that tomorrow.”
“How dare you…”
“Listen Liz!” he raises his voice now. “I have a plan. Next week we will haunt them down and we’ll kill them.”
“Next week? Why wait that long, Mason?”
Because of the full moon, when their powers will be at the highest level. But he couldn’t tell her that. He finally says “It’s personal.”
“Personal? Really? You talk like you know how to deal with vampires.”
“Just trust me, please. It’s only one more week. I need you to trust me. ”
“I don’t think I can do that anymore. My trust is gone. We’re attacking them tomorrow. That’s my final word.”
“Well, I’m sorry, but I can’t let you do that.” Mason changes his tone now, he’s more aggressive. He really can’t let her screw up his plans. The sheriff doesn’t like it at all.
“So what are you going to do? Lock me up in here like John Gilbert did? Come on, Mason! You’re more human than him.” Ha! The irony…
“You don’t know me that well.” he answers.
“I don’t care anymore. I’m really sorry this had to happen. But you are no longer wanted here or in the council. I think you should leave town.”
Mason walks close to her then he says, almost whispering: “You don’t tell me what to do. Nobody does. And yes, I can deal with vampires, because I know them. You can’t. And if you think you have any chance against them tomorrow, then just go ahead. Do whatever you want, but remember: when you face the consequences, there won’ be anyone there to help you.” We and the sheriff certainly haven’t heard Mason talk like that…ever. It’s quite shocking. The sheriff doesn’t respond. Mason leaves.