Peter Pettigrew story

I'm on the hunt for a really solid Peter-centric story. A lot of Marauder-era I read either dismisses Peter as absolutely pathetic or hardly acknowledges his presence. I would love a story that treats him as a true Marauder and shows a sort of downward spiral that leads to him going bad. Does anybody have any suggestions?

This is a fantastic one-shot about Peter's fall, if you want to call it that:

From Green to Brown by MerryD

The Slow Burn of Betrayal by Equinox Chick.

This was written for The Untold Story challenge. The characterisation is spot on and the entire fic quite chilling.