"Sirius! You traitor!" Lupin, usually so mild-mannered, had bloodshot eyes like a maddened beast. He drew his wand, ready to cast an Unforgivable Curse.
Wes reacted swiftly, blasting Lupin's wand away with an Expelliarmus.
Seeing the enraged Lupin about to transform into a werewolf, Dumbledore spoke up in time to stop him.
"Calm down, Lupin. I'm sure Wes will give us a reasonable explanation."
Dumbledore's words still carried weight. Lupin gradually calmed down, though he continued staring fixedly at Sirius, afraid he might escape.
Wes explained everything in detail and opened the Marauder's Map. Peter Pettigrew's name was clearly displayed upon it.
As one of the map's creators, Lupin knew exactly what that meant.
"Why is Peter still alive? Why is he at Hogwarts?"
Sirius stepped forward and looked at the incredulous Lupin. "I can explain everything."
He told everyone present about their decision back then to make Peter the Secret-Keeper.
At the time, he had thought it was a clever move, never expecting Peter to betray them and leak the information to Voldemort.
"How could this be?" Lupin could not believe that his former friend had endured such terrible misunderstanding and suffering.
"I'm not lying. You can use Veritaserum or examine my memories. I never betrayed James. I'm not a traitor." Sirius sounded almost pleading. He was willing to submit to any test; at that moment, he desperately wanted everyone to trust him.
Lupin gripped Sirius's shoulders tightly. "Why didn't you defend yourself back then? Why didn't you tell the truth?"
"James and Lily were dead. Voldemort had disappeared. Peter was 'dead' too. Only an arrogant fool like me was still alive." Sirius lowered his head, filled with self-reproach and guilt. He continued, "I entered Azkaban willingly. I was atoning for my sins."
Sirius's words plunged everyone present into