Walter White is a high school chemistry teacher who learns that he has lung cancer. With a new lease of life, Walter sets up a mobile meth lab with a former student and becomes a drug dealer in order to secure his family's financial security.

Following their debacle in the desert, Walter and Jesse are left with a mess to dispose of. Later, Skyler grows suspicious of Walt's recent activity.

Following an argument with Jesse, Walter is left to deal with Krazy-8 alone. After Marie raises concerns that Walt Jr is smoking cannabis, Hank shows him the dangers of drug use.

The DEA become suspicious of a new drug kingpin. Walt reveals that he has cancer to Marie and Hank. Elsewhere, Jesse visits his estranged family.

Walter and Skyler attend a former colleague's party, Jesse tries to free himself from the drugs, and Skyler organises an intervention for Walt.

The side-effects of chemotherapy begin to plague Walt, who is also cooking meth again, and Jesse's friend, Skinny Pete, introduces him to a distributor named Tuco, but things go awry and Jesse ends up hospitalised.