In the fourth-season opener, Nancy, Andy and the boys, on the run after she set fire to their house, head to the beach and a "heartwarming family reunion" with Judah's grandmother. They are met with a surprise, and a reunion with her irascible father-in-law (Albert Brooks). Back home, the cops grill Celia, and Doug and Dean finger her as the owner of the grow house.
Guillermo (Guillermo Diaz) tests Nancy by sending her on a drug-related errand south of the border; Celia's hard time in county lock-up gets harder when her cellmate decides to make Celia "her special girl"; Lenny heads to the track and leaves Silas and Shane in charge of bed-bound Bubbie.
Nancy gets a job working retail and finds it more enjoyable than she expected; desert-bound Andy has a tough time getting back home; a bee infestation has Silas and Shane hopping; Celia's relationship with Captain Till allows her to get closer to the action.
While exploring the tunnel at the back of the maternity shop, Nancy stumbles upon something she wasn't meant to see; Isabel moves in with Celia after Dean accepts a new job; Doug falls for a beauty he meets at the beach; Silas has a flirtation with Lisa (Julie Bowen).
When Guillermo cheats Nancy out of her cut from the operation, she goes over his head and appeals to the big boss; in Mexico, Celia discovers the joys of discounted medicine at the local pharmacies; Silas' relationship with Lisa (Julie Bowen) heats up; Shane finds some revealing photos; Andy and Doug take a big step in their human-smuggling operation.
Nancy and Esteban's impromptu get-together almost ends on a violent note; neophyte coyotes Andy and Doug smuggle their first illegals across the border; Silas admits to Lisa (Julie Bowen) that he's a marijuana grower; Celia develops an addiction; Shane's first day in his new school is a memorable one.
Nancy and Esteban try to work around their busy schedules to find time for each other, and now that she knows about Shane's fantasies and Silas's new, older girlfriend, Nancy has a sit-down with the boys; Silas and Lisa (Julie Bowen) add specialty items to the cheese-shop menu; Andy and Doug have a run-in with El Coyote in Mexico.
Nancy learns that Esteban's tunnel is being used for purposes other than drugs; Celia's family, fearful of her drug use, stages an intervention; Andy finds Maria in Mexico and brings her back across the border; Shane spends quality time with his two new girlfriends.
Nancy considers what to do about Shane's latest problematic behavior, and has another confrontation with Guillermo; Celia doesn't get along with her rehab partner (Bob Odenkirk) and she seeks a transfer to a new facility; Doug and Maria's relationship hits a snag, so they turn to Andy for help; Silas seeks Nancy's expertise when his new business takes off.
Nancy goes to DEA when she gets fed up with the dealings going on down in the tunnel; Celia gives rehab a shot and tries to make amends with her family. Also, Andy weakens and falls prey to Maria's charms; and Shane's ability to score drugs scores points with his new girlfriends.
The DEA brings Nancy in for questioning and she must come up with an explanation for Esteban (Demian Bichir); Celia ventures far into Mexico for a reunion with her estranged daughter (Haley Hudson); Silas has an encounter with Lisa's former husband; Doug realizes there are plenty of reasons for him to keep living.