Thomas has received the callback of his life to participate in a movie. However the callback day is the same day some of his friends are marrying. Now he's torn between lying to his friends to pursue the job of his life or losing the opportunity of a lifetime and attend his friends' wedding. Deceit shows up and puts Thomas on a trial to prove that Thomas is guilty of caring for himself more than he cares for his friends and prove to the other Sides that Thomas is not the perfect idealistic figure they think he is.

After Logan's abrupt departure, Thomas starts realizing that he cannot keep like that anymore, torturing himself with a love that cannot, and shouldn't, be back, because that wouldn't be fair, nor for him neither for his ex, because he wouldn't be happy with Thomas, just as he wasn't happy in the final times of their relationship. So, even though it's not going to be easy, and knowing that he's still gonna feel pain, maybe for a very long time, Thomas decides it's time to move forward with his life, accept that that love story is over for good, and, even if not healing completely from his pain, at least learn to live with it.

Thomas is feeling really sad over the remembrance of a long lost love he hasn't been able to move on from yet. He has the idea that going to Patton's room will help him enhance the happy memories to wipe away his sadness. So all the Sanders Sides and Thomas go to Patton's room, which is full of items of Thomas' past: things he wrote as a kid, music he used to play, gadgets he had and enjoyed, photographs and drawings of his life, and more. They all get carried away with the memories, while suddenly Virgil starts feeling bad. Only Logan notices this and tells the others they must get out of the room quickly, because "habitual worriers" like Thomas, with an habitual tendency to anxiety, when they look back to the past, they tend to think that the present pails in comparison to the "wonderful memories", which in turn worsens their anxiety.

Thomas has just dyed his hair purple, and the Sanders Sides, who as a result have also developed purple hair, show their opinion about the change. Patton and Roman love it, while Logan hates it and Virgil doesn't know what to say, as he doesn't want to spill too much anxiety on Thomas, since he wants to fit in the group, although he doesn't know how. When Patton has the idea that the purple hair reminds him of Nymphadora Tonks, from "Harry Potter", Thomas has the idea of using the Hogwarts Houses to sort all of the Sanders Sides into different houses based on their personality traits. As Thomas is a long time convinced Hufflepuff guy, the rest analyze themselves to see which house they would fit in, Gryffindor, Ravenclaw, Hufflepuff or Slytherin, and to try and get Virgil more integrated into the team.

Thomas and the Sanders Sides appear on Anxiety's room, which looks just like Thomas' apartment decorated as in a Tim Burton movie, with a clock that moves quickly backwards, spider webs everywhere, posters of "A Nightmare before Christmas" and a curtain with drawn spiders, something that scares Patton to death. At first they don't see him, but soon Anxiety pops up startling them all, a moment when Thomas goes back to normal. Anxiety tells them he has decided to quit, as he didn't thought he was wanted, and even though he only intended to protect Thomas, he has understood that he overdoes it and thinks Thomas will be better without him. Thomas and the others try to convince him to come back, as anxiety, even if unpleasant, is necessary for Thomas' life. But soon something strange starts happening to the Sanders Sides, as they start developing the same eye-shadow and progressively become more and more anxious the more time they spend on Anxiety's room.

Thomas is acting strangely, like an aloof moron without common sense at all. He doesn't take care of his hair or his clothes, he has no filter on what he's ready to say about his private stuff, he loses attention of what the others tell him, and even he has lost his fear of death and survival instinct and reflexes. Logan notices this and calls Roman and Patton for help. Soon they all realize that he has no anxiety at all, and when they call him, Anxiety doesn't show up. So they decide to sink down, all of them, Thomas included, into Anxiety's room, the corner of Thomas' mind where Anxiety resides, to find out what happened to him.

Thomas hasn't had any sleep the whole night, so he "wakes up" exhausted out of sleep deprivation. The reason he couldn't sleep is because of the anxiety he's had over the most bizarre intrusive thought about murdering his own brother which suddenly crossed through his mind while trying to sleep. It is soon that he will have to face a new Dark Side, The Duke, Roman's twin brother, who encompasses the part of Creativity Thomas constantly tries to suppress, the one that inspires on him such intrusive thoughts among other thoughts Thomas has been thinking that may be the proof that, after all, Thomas may not and may have never as angelic and pure as Patton wishes.

Thomas and the Sides are celebrating a belated Halloween by dressing up as different monsters. Virgil, disguised as a vampire, tries to scare his friends and fails terribly. Virgil realizes that Thomas and the Sides have embraced him too much as a friend, up to the point that they don't find him scary anymore. Furthermore, Thomas has told him that Virgil being scary was only a phase of him and an "act" that is over. So Virgil decides to make a journey with them through Memory Lane to remind them of all the terrifying phases Thomas has gone through in his life, so that he can remind them that he's still Thomas' Anxiety and he still can be terrifying if he wants to.

The Sanders Sides appear on Thomas because they feel in the mood for doing a video, and since it's Christmas Eve, and it's the first Christmas that Virgil spends with the rest of his new friends, Roman suggests that the four of them should wear festive Christmas "ugly sweaters" and perform a Christmas carol together. But they don't agree very much on the lyrics that Roman has written for them, especially Virgil.

Crofter's has partnered with Thomas to release a new fruit-spread inspired on Logan, so naturally Logan, as a Crofter's fan is flipping out about it. Roman, however feels a little jealous as he too wants his own flavor of Crofter's.

New year has arrived, and as suggested by Logic, Thomas starts thinking on New Year's resolutions. Creativity and Morality also pop up to give suggestions and in the turmoil of emotions, Anxiety pops up to remind him that it is pointless to waste time on New Year's resolutions because he's going to give up fulfilling them in a month or probably less.

Thomas has fulfilled one of the dreams of his life, appearing on a Disney show. So the Sanders Sides appear to ask him how the experience was.

Thomas talks about how he loves cartoons, and how he would love to be a cartoon. So, he decides to fly to L.A., meet Butch Hartman and ask him to turn him into a cartoon. He reluctantly does and for a minute Thomas and the Sanders Sides become characters of a day in the life of cartoon Thomas.

Thomas Sanders decides to take some time to figure himself out, and introduces three different parts of his personality: Logic, Morality and Creativity (also known as "Princey").

Thanksgiving is approaching and Thomas' dad, his real dad, has asked him to help cook the turkey. But Thomas still doesn't know how to cook, so Morality pops up and reminds him that he should improve on the process of becoming an adult, which he consistently calls "adultery", to Thomas' dismay.

Thomas is feeling quite relaxed, when suddenly Anxiety pops in and ruins his peace. He calls for help on Creativity, who suggests Thomas to retire to a corner of his mind for reinforcements. He does so, and Thomas and Anxiety pop up on Lilly Singh's apartment, where she gives Thomas a few tips to, if not destroying Anxiety completely, at least bring him down enough.