Over a thousand years ago, Hogwarts was founded. It was built far from prying Muggle eyes, for it was an age when common people feared magic, and witches and wizards suffered much persecution...
At some point during the war, Sirius and Remus began to distrust each other. This is how it happened. It starts in the Spring of 1980 and ends with the "death" of Peter and arrest of Sirius.