Stefan, Klaus, and Caroline begin their search for Silas at Professor Shane's office. Stefan believes that there will be something in his office that will reveal Silas's next move. Caroline jokes about the existence of an evil villain to do list that casually lists stealing blood and performing three massacres alongside more mundane activities like picking up dry cleaning. Klaus corrects Caroline and tells her that villains usually hire minions to pick up their dry cleaning. Caroline responds by sarcastically wondering why Klaus is necessary to helping her and Stefan find Silas. Stefan reminds her that they don't know what Silas is capable of, and therefore having an immortal hybrid like Klaus on their side could be beneficial. Klaus adds that he and Stefan work well together, referring to their time in the twenties. Stefan reasons that they did at that time because his emotions were off and Klaus explains that it's why Stefan was more fun. He also notes that Damon is probably relishing in Elena's emotionless state in New York. Stefan argues that Damon knows what he's doing. Klaus questions this and warns Stefan not to underestimate the allure of darkness; that even the purest of hearts are drawn to it. Seemingly impacted by his words, Caroline interrupts the conversation by introducing a book she found that might be of use. She opens the book to a section on expression triangles for Stefan and Klaus to examine. Stefan reads from the text, which states that in some types of magic, like expression, human sacrifice can be used as a focus for power. Two additional supernatural sacrifices can compound the mystical energy that creates an expression triangle. Caroline outlines the two massacres that have already taken place, emphasizing Klaus's hybrid failure in particular. Klaus points out that it wasn't exactly a failure before urging her to reveal what the third massacre needed is. It is revealed that witches are the third sacrifice.
Still in Professor Shane's office, Klaus and Caroline are now examining a map without Stefan. Caroline notes the locations of the two massacres that have already taken place with a marker, reminding Klaus once again of how he slaughtered twelve of his hybrids. She connects both locations with a line as Klaus smirks at her. Recalling that the book dictates that the expression triangle is equilateral, she predicts the location of the third sacrifice by completing the triangle on the map.
Amused, Klaus concludes that Caroline has been skipping her geometry classes. He argues that there are two possible locations for the massacre, as he completes a second triangle on the other side of the first triangle's base. In her defence, Caroline points out that Klaus didn't give her a chance to finish. They exchange lingering intrigued looks before Stefan returns to the office and informs them that he talked to Bonnie's dad and believes he's found Silas.
Later, Caroline is following Klaus in the woods as they use a map on Klaus's phone to track one of the possible sacrifice locations. Caroline demands to see Klaus's phone so that she can see where they are. Annoyed, Klaus reminds her that she did have the option of accompanying Stefan to the other potential massacre location. Caroline scoffs at this suggestion, explaining that she wouldn't leave Bonnie's life in his hands. Still frustrated, she asks Klaus if he even knows how to read a map.
Klaus informs her that he learned how to read a map from his friend, Magellan. She makes a sarcastic remark about him actually having a friend before wondering if he was drawn to his darkness too. Klaus states that he was referring to Damon and Elena when he made his earlier comment about the allure of darkness, but concludes that it struck a chord with Caroline. She denies that there is any allure to darkness. Klaus stops and turns to confront her. He asks her if she's never felt the attraction that comes when someone who is capable of doing terrible things for some reason cares only about her. Caroline acknowledges that she did once when she thought he was worth it, in obvious reference to Klaus. She continues by saying that some people can't be fixed; that people who do terrible things are terrible people. Visibly impacted by Caroline's harsh words, Klaus changes the subject back to the location of the sacrifice. Since there are no witches present, he concludes that they went to the wrong point.
They meet Stefan at the correct point where the twelve witches are attempting to cleanse Bonnie. Stefan informs them that the witches are linked and that Bonnie is going to kill them. This won't happen if the witches kill her first, Klaus points out. Caroline urges Klaus that they need to save Bonnie. He reminds her that the only way to stop the witches is to kill them, which would give Silas what he wants. With the witch ready to kill Bonnie, Caroline intercedes and drives the dagger into the witch's chest. This kills the witch along with the eleven other witches present. This puts the massacre location into darkness as Caroline ensures Bonnie is okay. Klaus and Stefan look on with shocked and defeated expressions.
Early the next morning, Caroline sits in shock as Klaus finishes burying the twelve witches who were sacrificed. Now that they are buried, Klaus concedes that it's almost like the sacrifice didn't happen, before he reminds Caroline that it did happen and now Silas has what he needs to destroy the other side. Caroline scoffs at his willingness to let Bonnie die.
Klaus argues that one sacrifice (i.e. Bonnie) is less than the twelve witches Caroline sacrificed, to which Caroline responds by emphasizing that the one witch she saved was her best friend.
Klaus replies by telling Caroline to say whatever she needs to in order to sleep better at night. The significance of what she has done begins to dawn on her in that moment and she becomes emotional. Klaus touches her shoulder reassuringly and notes that she looks like she is in need of comfort. She nods slightly and Klaus responds by telling her to find someone less terrible that she can relate to - referring to Caroline's earlier disparaging comments directed at him. Disappointed and hurt by his words, Caroline pulls away and leaves him with a regrettable look on his face.