Marlene+Remus I Voldemort was going after the Potters, and they went into hiding. They used a Secret Keeper. They were going to use Sirius, but at the last moment, they went with Peter instead, because Peter was a less obvious choice.
Peter gave them up. He gave up the Potters, Voldemort killed them both but Harry survived the Killing Curse. It backfired and killed him.
And ... Sirius confronted Peter, as I understand it now, and Peter faked his own death, killing thirteen Muggle bystanders. Sirius was arrested for betraying them all and sent to Azkaban.
For a year, I thought Sirius was responsible for all of this.
The war didn't end when Voldemort died. Death Eaters kept going, the Longbottoms were tortured, we lost more people, and [...] I don't know, I sort of lost touch.