Theory #1:
I think that the chopped up woman in the Toy Box is Zach's (aka Dana) birth mother.
(I say this because Paul said, "She tried to take you away from the only family that you've ever know". That would be weird to say, if MaryAlice/Angela was in fact, Zach/Dana's Mom). I bet that MaryAlice/Angela agreed to illegally "adopt" Zach/Dana. Then the birth mother showed up at their doorstep on Wisteria Lane, and evil Paul had to kill her, to avoid the secret from getting out!
I also bet that Mrs. Huber's Sister knows that something is up. I bet she knew Zach's birth mother, when the 3 of them worked together in Utah (Mrs Huber's Sister, MaryAlice/Angela and the Birth Mother).
What do you all think about that?!
And OMG...Gabrielle is going to be pregnant with John's baby!!
Theory #2
a somewhat extension of Theory #1...:
Paul had an affair with some woman (maybe a young woman, like college age), while he was married to MaryAlice/Angela. He and MaryAlice/Angela agreed to illegally "adopt" the baby (Zach/Dana). Then the birth mother had regrets, and tried to get reclaim Zach/Dana, and the birth mother ended up murdered by Paul. YIKES!
And...maybe the birth mother is somehow related to the Hubers, which is why Martha Huber wrote that note, "I know what you did, it makes me sick, I'm going to tell".
I wonder why Angela took on the name MaryAlice? Maybe MaryAlice was the name of Zach's birth mother?
This show is getting SO GOOD!