Sequel to 'Impossible - A potterlock fanfiction'. After their eventful first year at Hogwarts, Sherlock and John return to their studies and stay ahead of their classes. It all seems to be going fine. Until the fifth year, which is when Sherlock begins to get letters with all-to-familiar handwriting. What could it mean for the blooming young couple when an old face returns to their lives? And what threats could lurk outside Hogwarts, waiting...?