Those questions Evans poses to himself at the ending of the story may just be the very reason he pursues the mysterious matter to it's very end. In the manner such stories go, I assume someone is spying on Evan without his knowledge and that's where he's cautiousness becomes useful, which also makes him act as a restraining influence on Amina and Ji-Hoon. The truth is too precious to be rushed, it seems. They must dig slowly and cautiously until everything's uncovered. I don't suppose they've any other choice. Unfortunately, only Evan sees it that way.