Andrew Diggle is remaining loyal to Damien Darhk, even when there's no chemical reason for him to be doing so. Now, despite John's best efforts, the back-from-the-dead Diggle is remaining steadfast in his silence of his own due accord. Andrew believes this is the person he always was, John just couldn't see it. If that's the case, then he will never betray Darhk, and is going to spend an awful lot longer in that cell. You'd think, though, that there has to be a way of getting through to him, of breaking those ties to Darhk. If anyone can do it, it's John, but will he ever really get his brother back?