After joining the Order of the Phoenix, Sirius found himself roiling with mistrust and stress due to the great terror that was Lord Voldemort. It took its toll — by October 1981, he no longer trusted his old friend Remus Lupin, suspecting he was a spy and excluding him from important information. However, he trusted Peter Pettigrew implicitly, a decision he would grow to regret for the rest of his life. In 1981, the Potters were aware that Harry, along with the son of fellow Order members Alice and Frank Longbottom, had become Lord Voldemort's specific targets. Albus Dumbledore advised the Potters to go into hiding using the Fidelius Charm, which Dumbledore hoped would conceal them from doom. James was adamant about Sirius being their Secret-Keeper, believing that Sirius would willingly die rather than reveal where they were. However, believing Voldemort would suspect him, Sirius suggested a "weak, talentless thing" — Peter Pettigrew — as a less obvious choice. Keeping everyone else, including Remus Lupin and Albus Dumbledore, in the dark, Sirius and the Potters reassigned Pettigrew to be Secret-Keeper with Sirius as a decoy. On Hallowe'en night 1981, Sirius went to Pettigrew’s hiding place and found him missing. Unsettled by the lack of signs of a struggle, Sirius frantically sped to Godric's Hollow, discovering the Potters' house destroyed and his friends dead; only baby Harry was still alive. When Rubeus Hagrid appeared on the scene to take Harry from him on Dumbledore's orders, Sirius offered to take Harry himself as he was the chosen guardian in the events of James and Lily's death. However, Hagrid told him that Dumbledore had made arrangements to send Harry to Lily's sister, Petunia. Sirius conceded after an argument and gave Hagrid his flying motorcycle, telling him he wouldn't need it; nevertheless, after Hagrid had handed over the baby, he intended to return Black his bike, but never got the chance. After leaving Godric's Hollow, Sirius, overcome with grief and rage, tracked Pettigrew down, determined to kill him in vengeance. However, Pettigrew outwitted Black: confronted by Sirius on a city street, he shouted out that it was Sirius who betrayed the Potters, and then created a huge explosion on the street with a sing Blasting Curse, killing twelve Muggles in the process and enabling him to fake his own death and escape in his Animagus form, leaving a severed finger behind as evidence. The surviving Muggles who witnessed the event were pretty certain they saw Sirius murder their twelve companions and Pettigrew with the curse, and Fudge claimed to have seen Sirius laughing maniacally at the scene of the crime, suggesting that he thought Peter accidentally killed himself and found joy from that. Sirius was arrested by the Department of Magical Law Enforcement and sentenced by Barty Crouch Snr to life imprisonment in Azkaban without a trial for mass-murder with the Blasting Curse, giving the information about the Potters' whereabouts which lead to their death and service to Lord Voldemort. The surviving Muggles were Obliviated and given an excuse by the Muggle-Worthy Excuse Committee that a gas-leak occurred before they could remember who really cast the Blasting Curse, and Pettigrew was unjustly awarded the Order of Merlin, First Class for his confrontation with Sirius, which, along with the finger that they recovered, were "posthumously" given to his mother. As the time passed, due to misconceptions, many believed that Black drew his wand and killed Pettigrew before the other had a chance of even drawing. Even the other remaining Marauder, Remus, believed it was Sirius who betrayed their brotherhood. Marked as Prisoner ᛈᛉ-390, Sirius was placed in solitary confinement at the mercy of the Azkaban guards, the Dementors. Driven to the brink of madness, he retained his sanity by focusing on his innocence, which he said in the Shrieking Shack was "more an obsession than a happy thought"; it could not be detected by the Dementors, but still allowed him to maintain a sense of self and regain enough strength to transform into his Animagus form in his cell. Since Dementors have difficulty sensing the less complex emotions of animals, he was able to remain relatively unaffected as a dog. It was not at all trouble to them, though, since they thought it meant he was losing his mind like every other convict in their custody, including Bellatrix and some of her fellow Death Eaters. However, his brooding over his friends' deaths and Pettigrew's betrayal became an obsession as well. This was due to hearing many different theories regarding why Harry survived Voldemort's attack being made by the confined Death Eaters, the most persistent of which indicating that they believed Pettigrew to have betrayed them since the Dark Lord met his downfall on Peter's information. This most likely meant that Pettigrew went into hiding as a rat in hopes of avoiding the half of Voldemort's followers who avoided imprisonment, afraid that they will be motivated to kill him if his continuing existence became known, if not return to their master. Sirius waited until any sources reached within the prison walls leading to the discovery that Pettigrew was staying with a wizarding family as a rat to keep up on current news about Voldemort, all while getting very weak with no hope of driving the Dementors back without his wand, which was taken from him and stored away under Ministry of Magic safety repercussions. By 1985, Sirius' mother died, leaving the Black house-elf Kreacher alone in the house, which was thus left abandoned.