Caleb lowers his head when Peter starts teasing his sister. During their shared time in Amity Caleb has already had to be in the middle of those moments way too often, and he is tired of being pulled into them when he has no place to be there. At least when Four is around, he willingly steps between them and as soon as he starts arguing with Peter, Caleb has usually been able to just sink into the background and leave. Caleb hopes that the three of them won't start a big scene right in the middle of lunch, but before he can decide if it would be better to just go sit with some Amity people, Peter says something that grabs his attention.
"Besides I think we should all stick together now that we are all officially fugitives."
Before he can stop himself, Caleb has already raised his hand and is ready to grab Peter's shoulder. He catches himself and stops short, instead just nudging the other guy on the back as he asks: "Wait, what do you mean officially fugitives?"
There is a pause as Peter looks back at him, and Caleb can see that Peter wants to make a point out of Caleb shrinking back from touching him in front of Tris and Four. They've had that conversation many times and Peter still thinks it's ridiculous for Caleb to be afraid of what his sister would say, but so far he has agreed not to say anything in front of them. The couple has obviously had enough of Peter so they simply leave to find a free table, and like always, Peter and Caleb follow them.
The conversation quickly turns to Tris wishing to kill Jeanine, and Caleb can't keep quiet when he hears something absurd like that. He starts to argue with his sister, telling her that she can't just go around killing people, but Peter interrupts them because he can sense Caleb getting defensive over Erudite's actions and that is something that Tris should not hear her brother voice out. At least not yet, not while they still all need each other. So to pull the focus away from Caleb, Peter does what he does best, digs at a weak spot in Tris. He can feel Caleb giving him a warning look on his side, but Peter ignores it and just pushes until he gets a reaction. Tris jumps him and Peter ends up on the ground as a result, which was not how he planned it at all. Four stops the situation before it goes any further, but Peter is still annoyed that he let Tris get him like that and in front of Amity members as well.
Caleb helps him get the table off of him, and they make their way toward Johanna's office with Four keeping his hands on Tris the whole time like he is afraid that she might lunge at Peter a second time. Peter walks behind them, gathering his cool, and Caleb comes few feet behind him. Peter knows Caleb is watching him with a worried expression, but at the moment he is too annoyed to talk even to him. He plans to assure Caleb that everything is fine after they get out of yet another talk with Johanna, and thinks it is about time for him to ask when they will leave Four and Tris behind.