All for the sake of one little moonstone. How was Mason (Taylor Kinney) to know that once he got what he wanted that it would lead to his death? Whether it was going to be at Damon's (Ian Somerhalder) hand or Katherine's (Nina Dobrev) when she was done with him, Mason's days were numbered the minute Tyler (Michael Trevino) handed him the moonstone.

During the quest to secure the moonstone, Stefan (Paul Wesley) jumped into a well filled with vervain water, Damon shed his reformed bad-boy facade, Bonnie (Katerina Graham) and Caroline (Candice Accola) got past their differences, Elena (Nina Dobrev) and Stefan broke up for real, Jeremy (Steven R. McQueen) played Indiana Jones, Jenna (Sara Canning) stabbed herself, and Matt (Zach Roerig) became the latest unwilling helper for Katherine. Oh, and Mason lost his heart over a girl. But perhaps that can be blamed on Damon as he was the one who actually ripped Mason's heart right out of his chest.

As they all learned the hard way, once again, this is a battle to death. Katherine may be playing a game, but she is playing for keeps. When she promised that she would kill everyone in Elena's life if Elena and Stefan did not stay away from each other, Katherine meant it. Compelling Jenna to stab herself is just the beginning. Katherine already killed Caroline -- it was just lucky that Caroline had Damon's blood in her system so that she became a vampire and not just another corpse rotting in the graveyard.

Katherine also stabbed Uncle John (David Anders), but he managed to survive that stabbing as well. Katherine is actually having a pretty hard time killing anyone since all three of her attempts to kill someone close to Elena has failed so far. But maybe that is part of her infamous "Plan B." She does not actually need to kill anyone, for the murderous attempts were sufficient enough to finally convince Stefan and Elena that they had to break up.

Yet as any one can tell you, when you force someone to behave against their will under coercion or duress, it is only effective for so long. Eventually people will chafe under the undue influence and rise up to fight back against their tormentor. Katherine may have had over a century to strategically make Plan A through Plan Z; but in all that time, she never actually took into consideration how multi-faceted people are. They behave irrationally, without regard for themselves, and they will do anything to protect those that they love.

Katherine has but barely scratched the surface in discovering who she is really up against. Does she really know Elena, Jeremy, Jenna, Rick (Matt Davis), Bonnie, Caroline, Matt, Tyler or Liz (Marguerite MacIntyre)? Katherine may know Stefan and Damon, but the other inhabitants of Mystic Falls are likely going to be wild cards in her master plan. Let the games begin.

What Worked

Trust, seduction and fake promises. No one knows what anyone is really up to these days with so many lies being told to protect, manipulate and obscure the truth. We instinctively knew the second Katherine told Mason, "We'll live happily ever after -- I promise," that there was no way that she was going to let Mason live once he gave her the moonstone. People will promise you anything to get what they want. A promise is meaningless. Mason was only useful to Katherine so long as he could get her what she wanted.

It was also interesting how desperately Jeremy wanted to be a part of the cool kids' club. Rather than shun the vampire that tried to kill him, Jeremy offered an olive branch and told Damon about the moonstone. Is Jeremy playing a deeper game in order to destroy those who killed Anna? Or is he just looking for some sense of purpose and belonging in his life. He does not want to be standing outside the window staring in anymore; he wants to join the supernatural club.

Bonnie was also brought back into the club once she saw the vision of Mason kissing Elena, which Stefan quickly realized was not Elena. "You didn't see Elena. You saw Katherine." And Mason's dirty little secret was finally exposed. Rather than just forget about what she saw, Bonnie put aside her prejudices and joined forces with Stefan and Damon to capture Mason. As if that were not cool enough, she also reluctantly agreed to give Caroline another chance. It is nice to see Bonnie rising above her automatic hatred of vampires to work with them to banish a common foe.

Also having a nice mother-daughter bonding time were Caroline, the vampire, and her mom, the vampire-hunter. It was touching when Liz asked, "Are you really dead?" and Caroline softly responded, "Yes and no." While Caroline explained what her life is now like being a vampire, Liz got to see how much more strong and confident her daughter is, and she was genuinely proud of her. Thus, it was all that much more heart-breaking when Caroline had to compel her mom to forget everything -- even the fact that they were just starting to be friends.

Also turning over a new leaf, it was great to see Damon being a productive human being again, instead of a bitter vampire mooning over his lost loves. Pro-active Damon is a bit ruthless, but as he ripped Mason's heart out of his chest, one got the sense that Damon was doing it to save Mason from the pain of finding out that Katherine did not really love him. When Mason admitted, "I love her," Damon quietly replied: "I know. I've been where you are ... Katherine will only rip your heart out -- let me do it for her." Such a violent act would normally be off-putting and repulsive. But in this instance, one understood that Damon was being cruel to be kind.

Blinded by love, cursed by an Aztec curse -- Mason Lockwood's days were numbered from the day Katherine put him in her crosshairs. Damon was remorseful having to kill Mason; but he knew that it was kill or be killed, and Mason had already tried twice. It was only a matter of time. Plus, Katherine had her hooks in Mason, and he was not going to believe that she did not love him.

R.I.P Mason Lockwood. From the looks of it, both Tyler and Carol (Susan Walters) are really going to miss you. They have sustained too many losses, too soon.

It is also to Damon's credit that he survived finding out that the love of his life did not love him back. Damon is moving on. He is evolving. Perhaps knowing Elena saved him from the same fate.

So as Katherine cries for her lost werewolf, Elena and Stefan cried for each other and the love they were being forced to give up. Damon may have ripped Mason's heart out, but Katherine ripped out Stefan's and Elena's. Damon even tried to apologize to Elena for provoking Katherine, but Elena merely replied: "It doesn't matter. She won. Katherine won."

But winning is but a momentary illusion. They may not know all the rules and parameters of the game yet, but they all have more at stake than Katherine does. They all care for one another and will work together to take her down. Katherine is but one vampire frantically struggling to find an iron-clad bargaining chip to protect her against whatever is tracking her down.

What Didn't Work

What in the world is Katherine up to when all these atrocities are going on? Once she knew that Mason had the moonstone, she would not have let him out of her sight. His well being was of paramount importance to her -- at least until he handed over the moonstone. So what would keep her so occupied that she did not know that Mason had been snatched right from under nose? For an allegedly superior chess player, Katherine is looking like she is not paying attention to the game.

Giving Credit Where Credit Is Due

"The Vampire Diaries" stars Paul Wesley, Nina Dobrev, Ian Somerhalder, Steven R. McQueen, Candice Accola, Katerina Graham, Michael Trevino, Zach Roerig, Sara Canning, Matt Davis, Taylor Kinney. "Plan B" was written by Elizabeth Craft and Sarah Fain, and was directed by John Behring.

"The Vampire Diaries" airs Thursdays at 8 p.m. ET on The CW.