Mr. Pinter fired Lois because Dewey stole a bottle of cognac from the store. Even though it was Dewey who stole it and even after Lois returned it, completely untouched and unused, Mr. Pinter still fired her out of spite because Lois was originally up for promotion to manager and she refused. Out of anger, Lois ripped his toupe off of his head.
Later, Mr. Pinter offered to rehire Lois if she signs an apology letter to him. Lois refused and then told him that she knows a lot of terrible things that he's done including signing sales reports that she wrote for him, hiding a stash of marijuana in his left desk drawer and his affair with their boss (the district manager)'s wife. She tells Mr. Pinter off that he should be grateful that she is the only one who knows his secrets because someone else would've told on him a long time ago if they learned the truth about him. Lois leaves and Pinter thinks his secret is safe with her. Unfortunately, a smug Craig catches Mr. Pinter's attention. He turns around to see the grinning faces of the other employees who were listening in on the conversation between him and Lois. Their grins imply to Mr. Pinter that they intend to tell their boss about his mistreatment towards Lois along with his other bad deeds and his affair. He was so humiliated that he quit his job and never came back again.