Set post DOFP. Charles and Erik play a game of chess.

A brief glimpse into Erik's mind during DOFP to explain why he was so frustrated with Charles. Mild spoilers.

AU Charles Xavier is a highly prized CIA agent working to help put an end to the Humans Rights Activists and gain peace for the mutant race. Erik Lensherr is an HRA agent, working to bring down the mutants. When their worlds collide one evening, they are both forced to face a past they thought was long behind them, uncovering shocking secrets about the world they thought they knew.

Ten years after Cuba, Charles receives a letter from Erik. He doesn't take it well. Set both before and after DOFP, so spoilers to that. Rated for language and alcoholism.

Post DOFP: Charles finds Erik six months after the events in DC.

What does excuse him is the bullet you put in his spine. The overwhelming agony of watching his best friend and his sister walk away and vanish excuses him. The realization there was nothing he could do for anyone, that you were his greatest failure; that he tried harder with you than with anyone else and you left him the first chance you got excuses him. Rated for language.