Dexter Saul

Dexter Saul is a member of Bryce's Group and a survivor of the apocalypse introduced in Season 2. His injury during a run gone awry is what drive their group and the School Group together.

"Are We Okay?"
While on a run to a fire-station looking for fuel, Dexter, looking around, finds a door to what appears to be to another garage. Unbeknownst to him, the room is full of infected left behind and locked in. He manages to open the door and, to the group's horror, the infected pile in, setting off an alarm in the process. In their escape, Simon is bitten and while trying to save him, Dexter sprains his ankle. Pepper and Sam drag him away and the three are saved by Blake and the others.

After Claire has patched him up, Dexter wakes the next morning and learns that the two groups are going to be figuring out a trade deal. Dexter insists they leave as soon as possible and later that day, he, Pepper, Blake, Joely, and Claire all leave for the campsite.

"What Have You Done?"
Dexter is quickly taken to Patrick once they arrive at the campsite, who commends Claire for her treatment of him. Once the doctor leaves, the two talk and Dexter reveals his feelings of guilt over Simon's death, to which Claire tells him it wasn't his fault. Dexter then comments that the School Group has "been through some shit."

Pepper
Pepper and Dexter appear to be good friends. He backs her up and tells Simon to leave her alone when he jokingly makes fun of her and she appears worried about his condition when he twists his ankle.

Simon
Dexter and Simon appeared to have a good relationship. Dexter defends Pepper when Simon jokes around her, but Dexter goes out of his way to try to save him when he is bit. Dexter later tells Claire Rogers that he believes that Simon "didn't deserve to go out like that."

Sam
Dexter and Sam seem to have a good relationship. She is visibly worried about Dexter's ankle and goes out of her way to help him when they are surrounded by infected.

Claire
Following her medical care for Dexter, Claire appears to establish a good relationship with him. The two beginning open up to each other about their experiences following the outbreak.

Trivia
To be added...