The episode begins inside Caroline's bedroom, as she freaks out when she sees the bite on her neck - and even more so when Damon bares his teeth and attacks her again. But she seems quite happy to be dating Damon, telling Elena and Bonnie all about it, when she arrives at school. She's wearing a scarf to cover up the bite, and Damon clearly has her in some sort of trance.
Meanwhile. Stefan makes the football team and proves to be a great wide receiver, much to the chagrin of Tyler. Bonnie is also having doubts about Stefan, due to the feeling she got when she shook his hand last week (she described it to Elena as "death" and her psychic vibes grew even stronger this week).
To try and get her boyfriend and her BFF to get along, Elena invites Stefan and Bonnie over for dinner. It's actually going well, as Stefan is intrigued by the witch heritage present in Bonnie's family tree. But then Damon and Caroline crash the party.
Damon mentions to Elena that Katherine was killed in a fire and admits he also dated her. He almost seems upset about the loss. Later, while the girls are in the kitchen, Stefan tries to get Damon to back off, but he fulls admits that humans are hit play thing, to do with as he sees fit.
In order to protect Elena, Stefan gives her a necklace that contains the scent of a herb. It works to perfection because Damon tries to convince her that she wants to kiss him later in the episode - and she slaps him silly for it!
Prior to the football team's game, at a pep rally that featured a nice fight between Tyler and Jeremy, Stefan confronts his brother again. He says that he knows Damon hates him because Katherine is dead and he loves her; and that, Stefan says, is Damon's humanity. His response? He attacks and kills the football coach. Ouch!
Animal control is called, but Elena starts to suspect something is strange for the first time. The reason? Stefan was definitely cut while breaking up the aforementioned brawl, but he has no wound.
To conclude the episode, Stefan writes in his journal and comes to the realization that Damon is not human, no part of him is. He must be stopped.
Source: TV Fanatic