This episode features a lot of original plots. Coincidentally, just like the original episode about Bill in the previous season, this is also the third episode. However, this episode is quite important, with many details hinting that the subsequent plot will undergo major changes.
1.The opening hospital scene is an original plot. In the game, Ellie was not hospitalized; she was more severely psychologically traumatized, and this scene occurred shortly after Joel's death.

2.In the game, it was Tommy who told Ellie the information about Abby's group. But since Tina accompanied Joel on patrol in the previous episode, this part was changed to Tina revealing the information.
In this dialogue from the game, Tommy says he can't go for revenge and needs to explain to Maria, and this part is retained in the series.

3.In the series, a meeting was held in Jackson to discuss whether to go rescue Joel. Later, Tommy had a conversation with a psychologist, hinting at Ellie's behavioral problems. These are all original plots of the series.
In the game, Tommy did not explain the situation to his wife Maria. Instead, he left a letter and went directly to Seattle to seek revenge, asking Maria to keep an eye on Ellie and prevent her from going to her death. Helplessly, Maria had to let Ellie catch up with Tommy to help him take revenge together.
In the game, Tommy's desire for revenge was stronger than Ellie's, which affected a series of subsequent key plots (involving spoilers that cannot be revealed here). However, many people on Reddit felt that the plot in the later part of the game made Tommy OOC (Out of Character). Therefore, the changes in the plot here may imply that the subsequent plot about Tommy will also be modified (for another basis, please see the next point).

4.In the comparison of the previous episode, it was mentioned that the series reduced the number of members in Abby's team, resulting in the plot of a character named Jordan being added to Manny (the one whose face was scratched by Ellie).
At the end of the third episode, Manny appears in downtown Seattle, but he is dressed like Jordan (wearing a hat). This change seems minor, but it will actually have a great impact on Tommy's subsequent storyline (because Manny does not appear in Ellie's storyline but is related to Tommy). Therefore, it can be confirmed that Tommy's plot will be greatly changed.

5.In this episode, another villain organization of this season, the Scars (but they call themselves Seraphites), also officially meets everyone. This is a local religious group in Seattle that opposes modernization, advocates returning to nature, and worships someone called the Prophetess. All members have a scar on their faces and use whistles as a means of communication during battles, which are all reflected in the series.
They are also the main enemies of the WLF, the organization that Abby belongs to. The two sides have fought many battles in Seattle. In the series, this group of people was attacked and killed by the WLF (the "wolves" as they call them) while retreating.
But unlike the series, in the game, Ellie did not see the killed Scar members when entering the city. Instead, she was attacked by the Scar organization on the second day in Seattle, which made her realize the existence of this mysterious religious organization.

6.In this episode, on the way to Seattle, Ellie and Tina talked in the tent about the kiss they had on New Year's Eve. Ellie said she would give it a six, which made Tina a little unhappy.

Although this plot exists in the game, the details are completely different. First of all, this plot in the game first occurred on the day Joel was killed, in Eugene's cabin. But because the series changed Ellie's patrol partner that day to Jesse, this plot was also moved.
The biggest difference: in the game, it was Tina, not Ellie, who gave the kiss a six.

This involves a character setting issue. In the game, Tina has a more mature and humorous image. In contrast, Ellie seems a bit wooden and is always afraid that Tina will leave her. Therefore, Tina has always been in a dominant position in this relationship, and Ellie rarely teases Tina. But in the series, Tina's character is not as sophisticated as in the game, and their relationship has not been officially confirmed, so Ellie still teases Tina.