Stefan Salvatore, the lead hero in The Vampire Diaries, is the antithesis of his older brother, Damon, in that Damon embraces vampire ethics, while Stefan supports human ones. Where Damon sees nothing wrong with doing what comes naturally to a vampire; Stefan sees hypnotising, feeding off, and killing humans as immoral, and refuses to drink human blood, even though it seriously weakens his vampire powers and means he has to live with constant, strong hunger. Stefan chooses to live like a normal human as much as possible, while Damon prefers to live as a full vampire, and urges Stefan to join him. This difference in values creates a strong conflict between the two brothers that may be impossible to resolve; although at times Damon seems willing to meet his brother halfway, by at least partially complying with his wishes. Another way in which the brothers differ is that Damon’s attraction to Elena seems superficial (and he may in fact want her only to take her away from his brother), while Stefan genuinely cares for her.
Stefan (played by Paul Wesley in the TV series) has been a vampire for 145 years. He was turned in 1864, by Katherine. He and his brother, Damon, were in a love triangle with Katherine.
In 2009, Stefan has stopped drinking human blood and is attempting to live the life of a normal teenager.He has a special ring that protects him from sunlight. Stefan meets Elena at Mystic Falls high school, and is immediately attracted to her, due to her astonishing resemblance to Katherine.
After school, Elena meets Stefan at a cemetery, then he accompanies her to a local restaurant, where Bonnie invites them to a party that night.
When Stefan gets home from the restaurant, his relative Zack, who knows he is a vampire, accuses him of attacking a couple in the woods. Stefan denies it.Elena and Stefan arrive at the party together, but after Stefan sees her talking to Matt he retreats to the woods.
Elena sees Jeremy come out of the woods and assumes he's been doing drugs again. She goes after him to confront him, leaving Stefan at the party.
Theparty is disrupted when Vicki is attacked and left bleeding from a savage bite to the neck. Fearing that he knows who is responsible for the attack, Stefan finds that his older brother, Damon Salvatore has returned to town. Damon trys to persuade Stefan to resume his predatorial role as a vampire, and abandon his attempts to live a normal life. Stefan disagrees vehemently. They fight, and Stefan loses; Damon is stronger because he drinks human blood.
Matt and Elena are walking together on campus, talking about Vicki. Stefan is listening in with his vampire hearing. He hears Matt tell Elena that Vicki said the word "vampire" and then passed out at the hospital.
Stefan goes to the hospital and tries to use his abilities to make sure Vicki doesn't remember that Damon attacked her, but his attempt is cut short when Vicki's brother, Matt, arrives.Elena decides to go to the Salvatore house to talk to Stefan, but finds Damon instead. Damon reveals surprising information about Stefan's past, and when Stefan arrives home, Elena is confused and embarrassed to realise that he isn't happy to see her there.
At the comet party, Stefan shows up and Elena is surprised to see him. He apologizes for not being himself the day before. They talk about being hurt in the past and Elena thinks they are on the verge of breaking up.
When Stefan meets Elena’s best friend, Bonnie (a witch), Bonnie senses something strange about him without knowing what it is, but Elena ignores her warnings. Tyler tries to embarrass Stefan by throwing a football at him, but Stefan effortlessly catches and passes the ball back, impressing everyone with his skill. Mr Tanner reluctantly lets Stefan join the football team.
Elena invites Stefan and Bonnie to dinner, hoping that the two will bond, but the evening is disrupted by the unexpected and unwelcome arrival of Damon and Caroline. Stefan and Damon continue their duel for Elena’s affections. Stefan gives Elena a necklace with vervain in it to protect her from Damon. The next night, Stefan and Damon have a confrontation. Stefan tells Damon that he’s still human somewhere because he loved Katherine. To prove him wrong, Damon kills the football coach.
Damon enters Stefan’s dreams and makes him think he killed Elena. When he wakes, he returns the favor in kind by stabbing Damon in the stomach (which doesn't really do anything because they are, of course, undead). They start a knife fight which doesn't really go anywhere. Zack (the boys' relative) reveals to Stefan that he's been secretly growing vervain (an anti-vampire herb) in the cellar. Stefan tries to spike Damon's scotch with it, but Damon catches on and is angry.
Elena and Stefan go to the town's annual Founder's Party, where Damon tells Elena a story about the Salvatore family's past, leaving Elena with questions that Stefan refuses to answer.Later, Stefan reveals more of his past to Elena. He also takes action against Damon – poisoning Caroline’s blood with vervain, so that when Damon tries to drink it, he is incapacitated. Stefan locks Damon in the cellar of their house, in a room full of vervain to keep him weak.Stefan is hopeful that his plan to get rid of Damon is working, and decides to reveal parts of his past to Elena.
Elena realises Stefan is a vampire, and confronts him with her knowledge. Stefan admits what he is, and tries to explain, but Elena drives away. Stefan catches up with her at her house, and again tries to explain, but she tells him to leave, and he does.The next day, they meet at a café and Stefan explains that he isn’t the vampire that’s been killing people lately —Damon is. Stefan begs Elena not to share his secret with anyone for a day, and then make up her mind what to do with the information. Elena agrees.
Stefan takes Elena to the ruins of his old house and tells her how it all began: with himself, Damon and Katherine back in 1864.
Stefan and Elena return to Elena’s house, where Vicki is freaking out. Stefan knows what’s wrong with her straight away: Damon has started to turn Vicki into a vampire, and she needs to drink blood. Vicki runs into the woods, and Stefan pursues her. Catching up to Vicki, Stefan explains the choice she must make: drink blood and become a full vampire, or die.
A policeman tracks down Stefan and shoots him with a wooden bullet. Stefan falls to the ground in agony. Before the policeman can finish him off, Damon kills the cop, and pulls the bullet out of Stefan. Before Stefan can stop her, Vicki drinks the cop’s blood.
Stefan returns to Elena’s house, where she tells him she’ll keep his secret, but can’t be with him.When Vicki turns into a vampire, Stefan counsels her on how to control her hunger for human blood, but ultimately his attempts fail: Vicki attacks Jeremy, then Elena, and Stefan is forced to kill her by driving a wooden stake through her heart.
An old girlfriend of Stefan’s — Lexi, another vampire permanently locked in a teenaged body — comes to town to help Stefan celebrate his birthday. Shortly after Lexi’s arrival, the Sheriff interrogates Elena, Stefan, Damon, Jeremy and Matt about Vicki’s disappearance, (in episode 7, after Stefan killed her).
They all say that as far as they know, Vicki left town, and the Sheriff believes them. After the interrogation, Elena tells Stefan she can’t bear all the death and chaos that follows him around, and she’s breaking up with him. He doesn’t seem at all upset by this, which is surprising, because he tells Lexi he’s in love with Elena. Lexi brings Stefan and Elena back together again. Damon frames Lexi for murder, then kills her. This enrages Stefan, who swears he will kill Damon. Elena tries to talk him out of it, because she’s afraid of what killing his own brother will do to Stefan. It seems Stefan takes her advice, because after a fast, dramatic fight, Stefan puts a wooden stake through Damon’s stomach, rather than his heart. He says that as Damon saved his life once, he will now spare Damon’s.
At school, Stefan tells Elena he’s going to stay away from school, and from her, for her own safety. He knows that Damon follows him, and danger follows Damon, so apparently he hopes that if he stays away from Elena, Damon will too.
Elena tells Stefan about all the problems Bonnie’s been having with her amulet lately, and Stefan isn’t surprised — he gave the amulet to Katherine 145 years ago. Stefan promises Elena he’ll find out why Damon wants the amulet. Damon has promised Stefan he won’t drink human blood for at least a week, and the amulet gives Stefan an ulterior motive to play along with his brother’s attempt to make nice.
The two spend time drinking together, making fun of each other in a good-natured way, and even playing football with each other. Stefan asks Damon why he wants Bonnie’s amulet, and Damon tells him he wants to bring Katherine back: when Katherine was trapped in the burning church 145 years ago, she used the amulet to get out of the church and seal herself in a tomb beneath it. In exchange for the amulet, Damon made a deal with Emily, to help keep her lineage alive.
But the amulet only becomes fully charged with energy once every 145 years, when the comet passes overhead — this is the real reason why Damon came back to Mystic Falls when Stefan did. Stefan finds Damon pinned to a tree by a wooden stake driven through him by Emily, the spirit of Bonnie’s ancestor, now in posession of Bonnie’s body.
Stefan free's Damon, and they go after Bonnie/Emily. When they catch up to her, she tells them that she didn’t just seal Katherine underneath the church in 1856, she sealed up twenty-seven other vampires with her. Damon cannot free Katherine without freeing all of them, and Bonnie/Emily means to stop that at all costs.
Bonnie/Emily surrounds herself with a pentagram of fire, then throws the amulet above her head, where it explodes. Bonnie looks dazed as Emily leaves her body, then Damon rushes forward to take his revenge, biting Bonnie savagely in the neck and draining her to the brink of death before Stefan can pull him off her.
Stefan makes Bonnie drink his blood, and her neck wounds heal immediately. He tells Elena that as long as Bonnie doesn’t die within the next 24 hours, she won’t become a vampire. Elena loads Bonnie into the car and tells Stefan she’s going to tell Bonnie everything. Damon reveals that although Katherine compelled Stefan to love her, she never compelled Damon. He truly loved her, and now he can’t get her back, he’s leaving Mystic Falls. Stefan says he’s leaving too, since his attempt at living a normal life has caused so many deaths.
Elena begs him to stay, but Stefan says he must leave her, for her own good.