He was tricked by the White Witch into thinking that she was good and that the Lion and the talking animals were the evil ones. The Queen knew the prophecy of the four rulers too, so when she found out that Edmund had an older brother and two sisters, she had to kill them all. Using her magic, she offered Ed cursed food, which, once eaten, would make the person crave it all the more; forcing Edmund to do whatever it took to get more and more. She would do this to lure all four into a trap. His stomach would lead to their betrayal and death. At least, this was her evil plan.

Rumors, however, were flying that Aslan was returning and that the Witch's spell was already being undone. The first great sign of her breaking was the return of- you guessed it- Father Christmas. He gave to Peter a sword and shield, to Susan a bow and arrows, and to Lucy a vile of diamond filled with a liquid that can heal all wounds and sickness. He gave nothing to Edmund because Edmund had actually deserted his brother and sisters at this time and betrayed them to the White Witch, deceived by her cunning and sorcery and the aching pain in his stomach for more cursed food.