The central arc of the season focuses on Fiona's transition from the family's "emotional anchor" to a legal and moral outcast.
: After finding stability with a steady job and dating her boss, Mike Pratt, Fiona begins a self-destructive affair with Mike's brother, Robbie.
With Fiona in legal turmoil, the burden of leadership shifts to Lip, who is already struggling to balance his South Side roots with his new life at Chicago Polytechnic.