TURN, is a Revolutionary War drama about spies and a world without smart phones, neck ties and corporate cubicles. Damn good. I love a good period drama with period fashion, art design, gusty dialog and stabbing bloody bayonets.
Picking sides of a conflict destroys relationships, if discovered. A good spy is a nasty piece of work and perhaps personality. Submerged hatred of, or a profound love of a political philosophy drives a good spy to commit despicable acts if necessary. Of course it all depends on pov.
RE TURN: Lying to your father is a pretty tough act to pull off, but a good spy might offer up his mother, or the Queen, as a teasing gambit, but only if he can use her as a protected pawn in the game, eh?
Divided loyalties make a good double agent, and if a writer can handle a double agent , a good story.