|“|| Caroline: What if she can't forgive me?|
Stefan: She doesn't think there is anything to forgive. She just wants you to be with her.
— Stefan telling Caroline to spend time with her mom before she dies
THE MERGE — When Liv and Luke’s father arrives to town to celebrate their birthday, they try and convince him to let Jo and Kai take their place in the merge ceremony. After Tyler finds out that the merge is happening sooner than he expected, he urges Liv to let him talk to her father. Meanwhile, after Caroline’s plan to cure her mother takes an unexpected and devastating turn, Elena, Stefan and Damon gather at the hospital, while Jo attempts to save Sheriff Forbes’ life. Lastly, with the merge set to take place, Damon’s risky plan quickly sends things spiraling out of control, forcing one of the twins to take matters into their own hands.
|At her mother's house in the middle of the night, Caroline hears a weird noise and goes to investigate. Colin, the cancer patient Caroline thinks she cured at Duke, stumbles up to her door, covered in blood. She calls Stefan for help. He figures that Liz signed the house over to Caroline, and lets light in on Colin to test his theory. Colin's skin burns. He's a vampire. Which means after Caroline fed him her blood, he died.
Kai is hooked up to intravenous drugs that keep him knocked out at Jo's house. Damon comes to take a shift watching him. Alaric is off getting a mystical thingamabob to give Jo an edge when she goes up against Kai in the merge and Elena is off for a volunteer shift, wearing a new daylight ring from Jo.
Damon asks Elena on a date that sounds a little too perfect and she realizes it's one they've gone on before. She tells him he's cheating and suggests they have to start over from the beginning.
Liv and Tyler are cozy in bed when there's a knock at the dorm door. It's her dad, early to see her. And it's her birthday.
At the hospital, Jo sees a dead plant and tries to revive it with magic. It doesn't work, but Elena arrives intact, so the ring did. Stefan comes in dragging Colin. After some tests they see that Caroline's blood didn't cure him, it sped up his cancer and killed him. So he's terminal, but can't die. And since Caroline fed her mom her blood, the same thing is going to happen to her. Later, outside, Elena tells Stefan he should have known better.
Inside the hospital, Jo suggests they give Liz a complete blood transfusion of human blood. She doesn't have the magical ability to suck the supernatural vampire blood out of her.
Liv and Luke head to meet their dad to convince him Jo is strong enough to beat Kai in a merge. Tyler is pissed Liv lied about her birthday being two weeks away, now that she's 22 she's old enough to merge.
Back at the hospital, everyone waits for the transfusion to work. Caroline beats herself up for giving her mom her blood, but Stefan says Caroline's optimism is what Liz needs. They run to Colin's room when they hear him screaming. He's stabbing himself and wants to know why he can't die. He's in agony and can hear his tumors growing. He tells Caroline to just kill him. Damon rips Colin's heart out from behind, then tells Caroline the blood transfusion didn't work. She understands that he's saying that she killed her mom. Caroline disappears, leaving Elena to give Liz the bad news. Liz knows Caroline will never forgive herself.
Stefan finds Caroline picking out flowers for her mom's memorial service. He tries to convince her to come back, saying what she did, she did out of love. Stefan tells her about finding ways to avoid his own mother when he was young and she was sick. His dad sent her away and she died and he'd give anything to see her again. Caroline worries her mom won't forgive her, but Stefan assures her Liz isn't thinking that way.
Over dinner, Liv and Luke's dad isn't happy they don't want to merge. He tries to remind them it's their duty, but Luke doesn't want to kill his sister.
Damon returns to Jo's and finds Tyler trying to wake Kai up. At first he stops him, then Damon reconsiders. "I could kiss your right now, you beautiful moron," Damon says. Damon yanks the IV out of Kai and jams it in Tyler's neck, then calls Liv to talk to her dad. He says he has a bit of a Hail Mary. He asks about a celestial event happening today and if it would work for the merge. He tells Josh to get them to merge because Kai is about to wake up and be out on the loose. Kai wakes up, but all of his Traveler powers are drained away. Damon needs him as a "magic siphon."
At the hospital, Damon orders Kai to suck the supernatural out of Liz. Jo interrupts and Damon explains what Kai is up to. In exchange, Kai wants to merge tonight. Kai finishes with Liz, but she immediately starts to have a heart attack from the siphoning. Kai disappears and sneaks up on Damon to snap his neck. Kai takes Jo.
Outside after dinner, Josh Parker tells Luke and Liv how proud he is of them and takes their hands. Then he starts the merge. The twins are protesting when Tyler shows up and tackles Josh, punching him out. Luke walks off, telling Liv to trust him that that he'll be back.
Kai slices his hand open for the merge with Jo, and she goes along, promising to destroy him. They chant together in the quad but suddenly Jo is flung backward off her feet. Luke knocked her out and announces he's prepared to merge with Kai. Even though they're not twins, they share the same bloodline and are the same age after Kai's time in purgatory. Kai tries to bail, but Luke is strong enough to force him to merge.
In the hospital, Damon finds Elena performing chest compressions on Liz.
Luke and Kai chant as leaves whip around them. Jo wakes up. The lights burst out around them and their eyes go white, then both Luke and Kai fall over backward.
At the hospital, a doctor uses a defibrillator on Liz, who sees herself packing up a suitcase in a sunlit room, calling for Caroline to say good-bye. Even though he's compelled, the doctor says there's nothing more he can do. Caroline arrives and cries over her mother, whose heart has completely stopped. In her dream, Liz sees Caroline with her back to her. When Caroline turns around, she's covered in blood and full vampire. Liz wakes up with a start. Elena rushes out to get some air, freaked out that Liz almost died in her arms. Damon follows her. She kisses him, saying she doesn't want to waste another minute. When Liz wakes up, she assures Caroline none of it is her fault. When Stefan arrives, Liz sends Caroline out for coffee then makes Stefan promise he'll be there for Caroline after she's gone. Caroline hears it all from outside the room.
Back with Luke and Kai, Jo waits for Luke to wake up. Damon finds them. Jo is furious with him and blames him for the dire situation. Whomever wakes up is the winner. Back with her dad, Liv is freaking out that she can't reach Luke. Jo cries as she holds Luke's unconscious body, begging him to fight, wake up and come back to her. Kai also lies unconscious nearby. For a short while, that feels like forever, nothing happens. Then, Luke stirs and opens his eyes for an instant, giving Jo (& the viewer) false hope that he has defeated Kai and is the survivor. Back at Josh, he grabs Liv's hand frantically and tells her they have to run. He can feel that Luke merged with Kai and that Kai won. Jo realizes that Luke has slipped away and is in fact dead. Kai has after all won the merger. He stands up to gloat, then disappears.
- Antagonist: Kai.
- Elena has a new daylight ring made by Jo.
- Caroline learns that her mother Liz had signed over the deed to their house, which explained how Colin could enter the Forbes House without being invited inside by Liz herself.
- Colin Phelps arrives in Mystic Falls after dying with Caroline's blood in his system. It was then revealed that vampire blood does not actually cure cancer, but instead accelerates the cancer cells' rate of production. As a result, Colin's brain tumor grew to what Jo described as "Stage 10 cancer," which does not actually exist. Colin's accelerated cancer caused him so much pain that he begged Caroline to kill him after trying and failing to kill himself, and Damon ultimately ripped out his heart as a mercy killing.
- Jo tries to help Sheriff Forbes by giving her transfusion of human blood in order to stop the vampire blood in her system from causing the same effect on her as it did on Colin Phelps, but it doesn't work.
- Damon frees Kai after catching Tyler attempting to do it. Because all of the Traveler magic Kai absorbed had faded away, he was unable to use it to hurt Damon, Damon was able to make a deal with him-- Kai could siphon the magic that makes up vampire blood from Liz's system to save her life, and in return, he can use the magic he took in the merge ceremony against Jo like he intended all along, as there was a Mercury-Venus conjunction overhead.
- The fact that Kai siphoned the vampire blood/magic from Liz's system implies that Kai or another Siphoner could use their power to kill a vampire by siphoning the magic of their vampirism, much like the effect of the Magic Purification Spell.
- Elena threatens to rip off Kai's head if he doesn't get to siphoning off the magic in the vampire blood in Liz's body, and Kai jokes that she and Damon put the "fun" in "dysfunctional."
- Elena tries using CPR on Liz after her stops and Kai has siphoned off the magic of the vampire in her system.
- All the magic that Kai absorbed from the The Travelers spell has gone away while he's been asleep, this is seen when he tries to inflict pain on Damon.
- It's revealed by Joshua Parker that if the twins of the Parker bloodline don't perform The Merge before he dies, the Gemini bloodline will end, as the lives of all of the members of the coven are linked to their leader. He also mentions that the the traits of the weaker twin that dies in the Merge will be absorbed by the one who survives, that the souls of both siblings will unite into one new being.
- Joshua Parker tries to force Liv and Luke to merge to stop Kai, but he is stopped by Tyler, who knocks him out.
- Despite the fact that she is not strong enough to fight him off, Jo accepts to merge with Kai, refusing to run from him anymore.
- Luke intervenes in the Merge between Kai and Jo, and offers to merge with Kai instead. Due to the fact that his imprisonment had kept Kai at the age of 22 and that they were of the same bloodline, it provided the needed loophole to allow them to attempt the Merge.
- However, Luke dies during the Merge, and Kai absorbed his ability to possess magic, along with several of his personality traits.
- Damon tried to take Elena on a date that they have already have been on before during the "summer of their lives," which was first taking her to dinner and then to a theater where French films are playing and sit in the back of the theater and throw popcorn at the hipsters.
- Elena and Damon share their first kiss since Home.
- Originally Elena wanted to start over with Damon; however, after witnessing the near death of Sheriff Forbes, she chooses to resume where they left off, realizing that life is too short even if you are immortal.
- Elena doesn't speak French, even though she was taking French during her Sophomore year at Mystic Falls High School which is a class she took with Stefan as well as established in the Pilot.
- In real life Nina Dobrev speaks French as well as Bulgarian, making her trilingual.
- Joshua Parker was last seen in Fade Into You.
- This is the last appearance of Lucas Parker in the series, as he's killed in The Merge with Malachai Parker, but that doesn't rule out returning in flashbacks.
- Damon is the second vampire in the TVD series to have their neck magically snapped. The first was Elena in Woke Up With a Monster and by the same person, Kai.
- Elena is the first vampire to have two different witches make a daylight for her in either series.
- This is the first episode to feature Jo, but not Alaric.
- Colin Phelps is the second vampire unintentionally created with Caroline's blood that is killed.
- This is the fourth episode in the series to feature a birthday. In this episode, it's Luke and Liv's 22nd birthday.
- Colin Phelps - heart extraction, killed by Damon Salvatore.
- Lucas Parker - died due to being the weaker twin in the Merge, killed by Malachai Parker.
Behind the Scenes
- This episode had about 1.47 million viewers in the USA.
- Hashtag during the airing is #TwinMerge
- "Prayer For The Dying" is a song by Seal from his self-titled studio album released in May 1994.
- "Hipsters" are a subculture of millenials living in urban areas.
- "Witch doctors" were originally a type of healer who treated ailments believed to be caused by witchcraft.
- Elena to Damon: "If we're gonna do this, we can't just pick up where we left off."
- Stefan: "The blood didn't heal him. It sped up his cancer and killed him."
- Sheriff Forbes: "The same thing is going to happen to me."
- Caroline: "Why did I feed her that blood?"
- Stefan: "You took a risk. You did it out of love."
- Elena to Damon: "Life's too short. I don't want to waste another minute."