Let me Show you Heaven (слэш)

During Harry's sixth year, Dumbledore wants him and Snape to work closely together in order to defeat Voldemort. They become friends of a sort with mutual respect on either side, but they hadn't been prepared for everything Dumbledore wanted them to do.
Trying to make up for failing his best friend, Lily, Severus decides it's time that Harry Potter was given what he never had before: the truth.