Sylvestia Riddle and the Prisoner of Azkaban.

Spiel

"You're both mental." 

 "Ridiculous!" said Hermione faintly. 

 "Peter Pettigrew's dead!" said Harry. "He killed him twelve years ago!" He pointed at Black,whose face twitched convulsively. 

 "I meant to," he growled, his yellow teeth bared, "but little Peter got the better of me... not thistime, though!" 

 And Crookshanks was thrown to the floor as Black lunged at Scabbers; Ron yelled with pain asBlack's weight fell on his broken leg. 

 "Sirius, NO!" Lupin yelled, launching himself forwards and dragging Black away from Ronagain, "WAIT! You can't do it just like that — they need to understand — we've got to explain—" 

 "We can explain afterwards!" snarled Black, trying to throw Lupin off. One hand was stillclawing the air as it tried to reach Scabbers, who was squealing like a piglet, scratching Ron'sface and neck as he tried to escape. 

"They've — got — a — right — to — know — everything!" Lupin panted, still trying to restrainBlack. "Ron's kept him as a pet! There are parts of it even I don't understand, and Harry — youowe Harry the truth, Sirius!" 

 Black stopped struggling, though his hollowed eyes were still fixed on Scabbers, who wasclamped tightly under Ron's bitten, scratched, and bleeding hands. 

 "All right, then," Black said, without taking his eyes off the rat. "Tell them whatever you like.But make it quick, Remus. I want to commit the murder I was imprisoned for..." 

 "You're nutters, both of you," said Ron shakily. "I've had enough of this. I'm off." 

 He tried to heave himself up on his good leg, but Lupin raised his wand again, pointing it atScabbers. Lyn made to help. 

 "You're going to hear me out, Ron," he said quietly. "Just keep a tight hold on Peter while youlisten." 

 "HE'S NOT PETER, HE'S SCABBERS!" 

Ron yelled, trying to force the rat back into his frontpocket, but Scabbers was fighting too hard; Ron swayed and overbalanced, and Lyn caughthim am pushed him back down to the bed. Then, ignoring Black, Harry turned to Lupin. 

 "There were witnesses who saw Pettigrew die," he said. "A whole street full of them..." 

 "They didn't see what they thought they saw!" said Black savagely, still watching Scabbersstruggling in Ron's hands. 

 "Everyone thought Sirius killed Peter," said Lupin, nodding. "I believed it myself — until I sawthe map tonight. Because the Marauder's map never lies... Peter's alive. Ron's holding him." 

Their story made no sense whatsoever. How could Scabbers be PeterPettigrew? Azkaban must have unhinged Black after all — but why was Lupin playing alongwith him? 

 Then Hermione spoke, in a trembling, would-be calm sort of voice, as though trying to willProfessor Lupin to talk sensibly. 

 "But Professor Lupin... Scabbers can't be Pettigrew... it just can't be true, you know it can't..."

"Why can't it be true?" Lupin said calmly, as though we were in class, and Hermione hadsimply spotted a problem in an experiment with Grindylows. 

 "Because... because people would know if Peter Pettigrew had been an Animagus. We didAnimagi in class with Professor McGonagall. And I looked them up when I did my homework— the Ministry of Magic keeps tabs on witches and wizards who can become animals; there's aregister showing what animal they become, and their markings and things... and I went andlooked Professor McGonagall up on the register, and there have been only seven Animagi thiscentury, and Pettigrew's name wasn't on the list."