Frank returns, disrupting life; Lip attends college; Ian is missing; Fiona tries to connect with Debbie and Carl.

Frank stalks his previously unseen daughter, Sammi, and is surprised to find out she has a son, Chuck. Meanwhile, Fiona and Mike are getting serious. Also, Carl begins stealing dogs and holding them for ransom so that he can earn some drug money for Frank. Sheila has her first successful online date with Native American cowboy Roger Running Tree.

Against her better judgment, Fiona continues her secret affair with Robbie. The situation nearly boils over when Mike shows up at Robbie’s apartment while Fiona is inside. Fiona is able to hide just in time before her infidelity can be exposed. Frank, in increasingly dire health straits due to liver disease, attempts to contrive an “accident” that will provide an ample insurance payout to cover the cost of a potential transplant.

Fiona's series of bad decisions involving Robbie finally boil over. Meanwhile, Frank and Sammi pursue a cure for Frank's liver trouble and try to catch up on missed father-daughter time; and Lip gets a surprise visit at college from Army investigators.