Before Caleb was found by Ann, there was a scene where Ann was playing the piano and someone was watching her. John insisted it wasn't him so the obvious answer is Caleb was watching and studying them. Learning how to get closer to Ann. Even earlier before the piano scene, the dog began to bark at the closed front door at night suggesting Caleb was outside so maybe Caleb was lying about his religion to get close to Ann... Then Caleb's plan didn't go too well so he left knowing he can't beat John. Thoughts?
Well...we know he stole some eggs, but over how many days he was stealing them is not clear.
Also, he says that he was sick and was living in a nearby cave. Loomis detects some residual radioactivity on him but says that Caleb won't go through the same level of acute radiation sickness that he suffered. Although, I note we never see Caleb get sick at all.
As to whether Caleb left or not I can't say....but as to his plan, I have an idea: Maybe he was observing Loomis because he was truly intent on getting to that 'safe' town down south, Anson. ...and the only way he could make it through all that wasteland would be to have the use of the Loomis designed radiation proof safe-suit.
So maybe his plan was just to give Loomis every reason to let him just have the suit...and maybe the rest of the Nuclear environment survival cart that Loomis carried...and leave them in peace. So he aligns with Ann religiously against Loomis, charms her into giving him her affections, but also helps out with the wheel/generator project so much that Loomis would be in his debt...in a way.
So, in the end, if the question of going...as opposed to one of them killing the other...came to a head it wouldn't seem like a big deal to give what is possibly the most valuable piece of survival technology on the planet away to the last other man on Earth.
On November 6, 2012 god blessed America...again.
Caleb stole eggs and animals caught in the traps. He was observing Ann and John to see if they were friendly or radiated and crazy; can you blame him? Ann found him, so apparently he wasn't quite ready to approach them.
John was sicker than Caleb because he was submersed in radioactive water, throwing it on his face and probably ingesting or inhaling some of it. Caleb would have been exposed to radiation in a cave but not doused in it.
Good theory on Caleb leaving, but after watching this a few times, I had to reluctantly accept that John actually killed him. After Caleb was 'gone', there was a scene where John stood on the edge of the waterfall cliff, edging closer and closer to falling off. He was trying to resolve his guilt with his need for companionship survival. Had he not succeeded, he would have jumped.
Ann, too, was trying to resolve her feelings towards John, about what he did. She, too, contemplated suicide which was symbolized with the glass of water she pushed along the table with her book, eventually pushing it over. They each were at a breaking point where they had to decide whether to live, not just survive, or to kill themselves to end their misery. If they decided to live, they would have to find a way to forgive and accept each other, John for killing Caleb, and Ann for 'betraying' John. In the very last scene where she starts to play the organ that John moved into the barn, she turns and gives him a very, very subtle grin. And he in turn gave a subtle nod of comprehension. By moving and preserving the organ for her was an apology of sorts: to finally show her respect and appreciation for her, and for her to understand that what he did to Caleb was for her, for them. I don't think John was a bad person; I think he just didn't want to end up alone even though he kind of already was a loner. Being a loner and being completely alone are two very different things.
Good movie. A lot to contemplate with a totally hot cast.