Skirmish in Chicago

The Skirmish at Chicago was the first major conflict between the Winchester Family and demons.

Background
Sam and Dean picked up a case on a string of murders of people coming from their hometown, Lawrence, Kansas. Azazel's daughter possessed Meg Masters and tracked and kept an eye out for Sam for several weeks since the two of them met at an Indiana bus stop. The demon's goal was to capture the Winchesters for Azazel's plans, which were yet to be revealed at the time. It would later be revealed after several more conflicts that this skirmish was only a part of several plans of Azazel that would ultimately lead to Lucifer 's release.

Battle
After Sam and Dean realized Meg was summoning and controlling a shadow demon called a Daeva, they attempted to subdue her. The demon knew that the hunters were after her and she revealed it was her plan all along for them to come to her apartment. She then summoned the shadow demon to attack the brothers. Once they were wounded, she had them tied. The demon tried to seduce Sam while Dean attempted to escape. However, Dean's plan was foiled when Meg noticed him attempting to escape. Unbenknownst to her, Sam was also trying to escape. Before she coudl stop Sam, the hunter already destroyed the altar, releasing the Daeva from bondage. The Daeva then turned on its former master and dragged her out of the window, dropping her several stories into the concrete below.

Sam and Dean escaped on the Impala and went back to their motel room. Without notice, John revealed himself to his sons. Before they could catch up properly, they were assailed by several Daevas. All three suffered sever but non-fatal wounds before Sam lit up a flar that destroyed the demons.

Aftermath
The Winchester family concluded that it was best for them to work apart because they thought their relationship with each other made them weaker in battle. The demon possessing Meg would regroup with her father Azazel and her brother Tom.