|“||We'll live happily ever after. I promise.||”|
They were first seen at the end of Kill or Be Killed as lovers. When Mason was killed by Damon in Plan B, Katherine was upset because her plan had failed and she could no longer use Mason to get the moonstone. It was clear that Mason loved Katherine but didn't trust her, as he hid the moonstone at the bottom of a well filled with vervain. Katherine obviously did not love him, as she was just using him.
Throughout The Vampire Diaries Series
Katherine and Mason's relationship was revealed in Kill or Be Killed at the end of the episode. They kissed passionately in an Aston Martin as Mason told Katherine he had gotten the moonstone.
In the following episode, Plan B, Katherine and Mason are seen making out in a bed. He promises to get the moonstone for her, unaware of Katherine's true intentions to hand him over to Klaus to be sacrificed as the werewolf in the ritual. The moonstone is later found in a well full of vervain, and Damon kidnaps Mason and takes him to the Salvatore Boarding House, torturing him for information. Mason reveals enough, and Damon rips Mason's heart out. Katherine later finds out via a phone call, and promises she has a Plan B.
- Season 2
- Katherine: Mason? What happened?
- Mason: Jimmy attacked me.
- Katherine: What? Why?
- Mason: He said that I hit on Marla.
- Katherine: Why would he think that?
(Katherine embraces him)
- Katherine: I told you to stay away from them.
- Mason: Why do you even care?
- Katherine: I don't want you to get distracted. I need you to find the moonstone.
- Katherine: You got it?
- Mason: I got it.
- Katherine: Where is the moonstone?
- Mason: Somewhere safe.
- Katherine: Don't you trust me?
- Mason: I don't trust anyone.
(Katherine bites his neck)
- Mason: What happens once I give you the moonstone?
- Katherine: We'll live happily ever after. I promise.
- Mason: I'll bring it tonight, I promise.
- Katherine: You know I love you.
- Mason: I love you too.
- -- Plan B