En-dor was 4.5 miles northeast of Shunem, so it was on the other side of the enemy from Saul.
(The ESV Study BibleTM, English Standard Version (ESV) by Crossway Bibles, 2007. Page 536)
The Medium at En-dor
Saul had put the mediums and the necromancers out of the land of Israel. (1 Samuel 28:3) But when he was terrified of the Philistine army and received silence from the LORD, he said to his servants, "Seek out for me a woman who is a medium, that I may go to her and inquire of her." His servants suggested the medium at En-dor.
Saul disguised himself and went with 2 men at night, asking her to divine for him by a spirit and bring up for him whomever he shall name. She was cautious, since it was illegal, but he said, as the LORD lives, she shall face no punishment. She asked who to bring up, and he requested Samuel. When she saw Samuel, she screamed, but Saul had her describe him. "I see a god coming up out of the earth." ... "An old man is coming up, and he is wrapped in a robe." Saul bowed and paid homage to Samuel.
Samuel asked why he was disturbed, and Saul told him about the Philistines and silence from God and that he needed to talk to him. Samuel told him he did not obey the voice of the LORD against Amalek, so He has become his enemy. The LORD will give Israel into the hand of the Philistines, he and his sons shall be with him, and the LORD will give thee army of Israel into the hand of the Philistines.
Saul fell on the ground with fear and had no strength left. The woman humbly but insistently fed him, though he said, "I will not eat." She killed a fattened calf and baked unleavened bread for Saul and his servants, and they left that night.
(1 Samuel 28)