It took place after Harry Potter finished his first year at Hogwarts. He asked Dumbledore not to make him come back to the Dursleys but didn't tell him how bad the abuse was. Dumbledore just thought that it would be a chance to create a better bond between Severus and Harry. Therefore, he sent Harry home with Severus...
When young Harry Potter gets wrongfully convicted of murdering the Dursleys at the end of 2nd year, there are only two people willing to defend him -- Remus Lupin and Severus Snape. Despite their efforts, the 12 year old boy was sentenced to Azkaban without so much as a second thought. Two years later, when undeniable...