In order to rid the world of vampires, a clan of Celtic witches has arrived in Mystic Falls, seeking the help of Bonnie to complete their plan. Bonnie deceives the witches by using human blood, that of Jeremy's, instead of vampire blood, in the spell. The ghosts of the Mystic Falls dead witches drive the Celtic clan away for tampering with the balance of nature.
After Bonnie casts the tampered spell, all the vampires of the town collapse into what looks like death. Suddenly their bodies change in color and a warm glow appears. The vampires awake as humans. The Mystic Falls witches tell Bonnie that her spell is only temporary and that the vampires will remain human for twenty four hours, after which they will return to being vampires.
In this 24 hours, Stephen deals with his guilt as a vampire and wants to feel all the pain his vampire self deadened. Elena wants to be by his side as a human, yet Stephen refuses. Elena finds Damon in a nearby park, swinging in the sunlight smiling. He looks happy and peaceful and tells Elena how much he has missed being human, being so at peace, that all the anger inside of him wasn't boiling to the brink of destruction. Elena and Damon go for a hike where they have a heart to heart. At the end of their hike, they kiss as humans and Elena suddenly this is who she loves- the human side of Damon. They spend the rest of the evening with one another.
On the other side of town, Carolyn and Tyler spend time with each other and decide each want to see their parents as humans again. Carolyn reconciles with her mother and Tyler with his mother. Maternal bonding ensues, tears of joy and sadness.
Bonnie's mother calls Bonnie up so they can see each other. Bonnie and her mother meet at Bonnie's house and try to reconcile their differences as well.
Elena sleeps over in Damon's room of the Salvatore Mansion. She awakens in the middle of the night to find Damon's skin is cold again and he is no longer human. She sneaks away to Stephen's room where he is awake, brooding. Elena sits down with him and Stephen explains to her why he had to be left alone. How he had over a century of bloodlust, guilt and pain to ponder in just one day as a human. That part of him needed to be forgiven as a human. He says to her that he feels much more like himself now, that his bloodlust felt at ease. Elena and him hug and when Stephen tries to kiss Elena, she pulls away. Stephen nods his head and sighs. "It's Damon isn't it. You've got feelings for him don't you?"
Elena takes in a deep breathe. "Spending time with Damon as a human made me realize, that part of him is still alive, that humanity and love that he has- I, yes, I love that part of Damon..."
"Are you in love with him Elena?" Stephen asks.
At that moment, Damon walks into the room, grabbing his chest. "Something's wrong..." He falls to the ground.
"Damon!" Elena shouts.
As Stephen jumps up to see if his brother is okay, he too starts to fall to the ground. "I, I can't breathe, Elena," he mouths before tumbling over.
On the other side of town, Bonnie watches as her mother spasms and falls. She realizes something is wrong with the spell and quickly looks through all her witch books to find something to help. Jeremy shows up at her door, with the ghosts of Ana & Rose by his side. They are telling him that his blood wasn't purely human blood, that his paranormal gift has changed the spell. Bonnie needs pure human blood, free of anything paranormal, to undo the damage. Bonnie calls on Matt to get his blood and complete the spell with pure human blood. When she does this, her mother returns back to her normal vampire state.
A frightened Elena tries to awaken both Damon and Stephen, who lay on the fall barely moving. They suddenly awake, and seeing both of them are okay, Elena sits down by Damon's side first to check on him. She turns to Stephen who simply nods at her, as if he is okay with her feelings for him, that he almost expected this to happen.
"You're both okay, you're both, vampires again?" she says slowly.
Damon looks up at Elena and Elena looks a bit taken aback. His eyes somehow look more human. "I'm fine," he says glumly. "Hungry, but fine."
Stephen gets up and offers to bring back some food for Damon and him. Damon thanks Stephen who leaves Elena and Damon alone in his room.
The episode ends with Elena and Damon sitting on the end of Stephen's bed. Elena looks into Damon's more human eyes, thinking about what she had said to Stephen, that she loved the human side of Damon. She reaches for Damon's now cold hand and holds it.
"Elena," Damon starts.
"You don't have to say anything," Elena says. "I know. This must be difficult, for both of you, to have had a day as a human and now..."
"Yesterday was the happiest day of my life, Elena," Damon says softly. "I got to be with you, as a human... I'll never forget that."
Elena smiles, eyes tearing up and leans in to kiss Damon. They have their first tender, mutual kiss, a kiss that means more than just friendship.