Satan begins his temptation of Eve by disguising himself as a snake and leading her to the Tree of Knowledge of Good and Evil. Here, the disguised archangel tells Eve that he has learned to speak after eating of the forbidden fruit -- to which Eve laments and says that she cannot eat from the tree. Satan then tells the woman that he has become humanlike because of his eating of the fruit and that she will similarly become godlike. The adversary goes on to say that God would not punish her for eating the fruit anyway, and would instead praise her dauntless courage (for defying death in order to attain knowledge). Satan says that God could not punish Eve for such a petty offense and that there is absolutely no wrong in seeking knowledge (an argument that may convince Eve, as she has just recently seen how fervently Adam sought knowledge from Raphael). Finally, Satan convinces Eve that God would not punish her because it would be unjust and that if God is unjust, he is no God at all.
Afterwards, Eve gives her own reasons for eating of the fruit. She says that she would become equal, if not superior, to Adam after eating the fruit-- which would make him love her all the more. The poem climaxes as Eve takes the first bite of the forbidden apple, and Satan slinks away. Paradise laments, and Adam comes to find Eve.
Adam is shocked to see that Eve has eaten from the tree, and is clearly upset. He laments his fate since, if she is damned, then he is too (as his love for her makes them one). Rather than being convinced to betray God as Eve was, Adam simply eats the fruit so as to stay with Eve -- whether it be in life or death.
With that, the fate of Man is sealed and the pair consumate their sin in passionate, lustful embrace.