This story is an AU. Sebastian Black-Lupin is the child of Sirius Black and Remus Lupin. Now, in his fifth year at Hogwarts, with his best friends, Harry Potter, Hermione Granger and Ron Weasley. This year changes everything as feelings get the better of them and things change, no one can really tell whether for good or bad, but Sebastian's always had a lock on, now it's time to find the key.