The panty baroness fell from grace this season. Her bodyguard roommate betrayed her and she clashed with Maria, eventually forming a security group, which was basically white supremacists. Fall from grace, we told you. As the panty empire crumbled, Piper was branded, but with the help of Red's family (Norma, Nicky, etc.) they changed the swastika to a window pane. Oh yeah, she also smoked crack in the garden.
You may recall season three ended with Alex's fate in question, well, she survived. And eventually killed her attacker with the help of Lolly, but this then presented Alex with a problem: Lolly was unstable. She could reveal the murder and ruin what was already a depressing existence in prison. Meanwhile, Alex, Nicky and Piper smoked crack in the garden.
After getting off janitorial duties, Taystee became Caputo's assistant and gained access to… the internet! She tried to sell a picture of Judy King to the tabloids. Following Poussey's tragic death, Taystee urged Caputo to call Poussey's father and do the right thing while making the statement to the public about her death. When he doesn't, Taystee helped spark the riots.
When not dealing with her lack of sleep thanks to a snoring roommate, Red was battling Piscatella and advising Alex what to do with Lolly and the whole dead guard situation. She formed a bond with Healey, but that quickly turned. Later in the season, Red and her family got back together to turn Piper's branding into a window. Piscatella's cruel treatment of of Red eventually unites the inmates and they stand on tables in protest, which then resulted in Poussey's death.
After escaping with Maureen at the end of season three, the two are eventually brought back and the relationship between the two quickly soured, eventually Humphrey incited a fight between the two of them. Viewers also learned about Suzanne's tragic backstory and that she was in prison following the accidental death of a young boy she befriended.
Thanks to Judy King, Nicky returned from maximum security, but she was back on drugs thanks to Stella. Before she left max, she came across Sophia and gave her what little human contact she could. Back at Litchfield, Red's breakdown caused Nicky to kick the drugs again.
Following the events of season three, season four began with Sophia in SHU, "for her own safety." Eventually, Nicky, who was sent to maximum security in season three, came across Sophia and slipped her a magazine, which she then used to cut herself. Her attempts to leave SHU were fruitless until her ex-wife finally got wind of what went on and raised enough stink to get her transferred back. She mended fences with Gloria, the reason she was in SHU in the first place.