Adam fell from his Divinely appointed position in the chain of authority. This was Elohim first and foremost, Adam and then Eve over the “fish of the sea, and over the fowl of the air, and over the cattle, and over all the earth, and over every creeping thing that creepeth upon the earth”.
In listening to Eve Adam fell from his position and in effect turned the chain of Divinely appointed authority on its head. Eve trusted the serpent and Adam trusted Eve.
This is where Adam fell from and not from grace.
The effect of the fall was devastating. At that moment Adam lost his innocence and became guilty, he knew shame and hid. Adam brought forth Seth in this image of guilt rather than innocence. It was necessary for the Last Adam to be innocent and that He was, without spot or blemish.