The sequel is no longer available to read, due to it being removed from FF.net. It was never completed.
There are bits and pieces, but unfortunately there was no official plot (or nobody knows the main plot) From what has been read:
-There was supposed to be a prophecy, most likely about one (or both) of the twins.
-Most likely, Firepaw and Angelpaw were to fall in love and have kits. Unknown if it actually happened.
The main characters are twin sisters named Crimsonpaw and Angelpaw. Crimsonpaw is a black tabby with red eyes, and Angelpaw is a white tabby, eyecolor unknown. Their parents died/vanished and the twins were adopted by Moontree.
A few honorable name mentions are:
And a few others.
An entire collection of everything wrong with this fic can be found on the TVTropes page.