Originally Posted by atm0073
I may be wrong, but I believe the "clue in the mystery" achievements are slightly glitched. To get them, I think you need to play through the game with an uninterrupted save. Because I have the game completed on Legendary, but do not have the Super Sleuth achievement, I am assuming this is so.
same happened to me, took 1 break through the whole campaign on legendary. let me know if you playthrough again and unlock it?