Why did Peter go to Albania and restore Voldemort to power instead of, you know, running away? Why not find a distant corner of the globe where no one would recognize him and where the long arm of Dumbledore didn’t reach and live in relative peace?
Well. Remember what Remus said while literally rolling up his sleeves to murder Peter?
“You should have realized, Peter […] If Voldemort didn’t kill you, we would.”
What would Peter be thinking once he got far enough away to catch his breath?
“Uh-oh, Dumbledore might actually believe Moony and Padfoot and the kids when they tell him I’m still alive and the real traitor. What if he clears Padfoot’s name, or at least helps him escape? Won’t that leave Padfoot at liberty to hunt me down? And it’s almost the summer holiday—Moony will be able to join the hunt in a couple of weeks. And no one’s taught DADA two years in a row in my lifetime, and where else is he going to get a job now? I’m going to spend the rest of my life looking over my shoulder for those two. If I’m lucky. They might actually find me! What options does that leave me?”
You’d think that working for Voldemort is such a terrible job that living on the run while fearing every shadow is a big black dog doesn’t sound that bad by comparison. There’s no Cruciatus, as long as he doesn’t get caught. On the other hand, Sirius is the guy who tricked a fellow student he didn’t like into entering a tunnel with a werewolf. And none of the Marauders ever actually confirmed that Remus
wasn’t a willing participant in that plan. Why was he rolling up his sleeves in the Shrieking Shack if he was only planning a quick, clean death? Maybe Peter sincerely believed that whatever Sirius and Remus would do to him was so terrible, and living in fear of it so unbearable, that Voldemort didn’t automatically look like the worst choice.
And why didn’t Dumbledore send Sirius after Peter? Um. I’m sure we would all like to think that Sirius, unlike Quirrell, would be protected by plot armor if he ended up in Albania and would never return to Britain with a spiffy new turban. Or a motorcycle helmet and a sudden obsession with traffic safety. But…well, would
you want a Voldemort with all of Sirius’s cleverness and skill at nasty curses to draw on? Me neither.
How he convinced Sirius not to hunt Peter is another question. Though did
Sirius know Voldemort was in Albania? Maybe Dumbledore, ah, neglected to mention that, and Sirius was grimly hunting tropical islands for rats between replying to Harry’s letter and drinking rum.