This is definitely one of mot more favorite flash series here on NG, but you could use some tweaks.
Some more principles of animation and design could be applied. more on the design stand point than the animation. Much of your backgrounds are too clean, you gotta rough them up a little, makes them more realistic, same with a few aspects of your characters.
Lastly I have a slight issue with the voices in this one. usually I don't have any complainants. But this time it seems like your voices were just saying the lines, they weren't putting any feeling in to them. You gotta fix this, fast.
other than that great story, I hope to see more, and soon.