(Season 2 spoilers ahead)
In season 2 of Fringe,
Charlie Francis finds himself alone in a hospital boiler room with a shapeshifter in the form of a nurse. The shapeshifter kills Francis and takes his form. When the other agents arrive, he is standing over the body of the shapeshifter/nurse. This body's blood is later analyzed and found to be human.
Yet later on Francis burns a third, identical body. Am I missing something about the mechanics of shapeshifting? If not, where did this third body come from?
I cannot quite follow the explanation given in the wikia article:
...hid his body in the dumpster, substituting his body for the body of the nurse that it had killed earlier, thus seemingly killing itself.
It couldn't be the original (real) nurse's body -- there was not enough time to retrieve it.