Crimson Moon is a private consultant for anypony with the money to pay him, more of a detective in a sense. If you need something found or a crime resolved, he is the stallion to call. Having been taken in by Luna as her protégé, he has even worked with the Princesses on a number of occasions.

All of his skills are put to the test when he is called on upon Celestia, who has news so important that not even her sister or Twilight knows. A crime so heinous, the penalty is banishment from Equestria… or even death. Because murder is no forgivable act against ponykind. No murder had been committed in over a hundred years, so naturally, he takes the case and agrees to bring the killer to justice.

Except… not everything is as it seems. A troubled past, one of which he can't even remember, begins to reveal itself to Crimson. As visions of his unknown past begin to creep into his mind, he begins to fear that he himself is intricately involved in the murder more than he'd ever want to be.

And on top of it all, he finally finds himself face to face with a mare that'd been haunting -rather, gracing- his dreams for two years. As his own self doubts and fears begin to come to fruition, he knows she'll still always be there for him. They promised each other they would be, after all. And promises… they mean more to him than memories, anyways.