With the fall of Gus Fring’s (Giancarlo Esposito) drug empire, Walter White (Bryan Cranston) and Jesse Pinkman (Aaron Paul) must pick up the pieces and ensure they’re not linked to any of the former crime lord’s dealings. To do so, they must destroy incriminating evidence on Gus’s office laptop, which has been confiscated by the investigating team of police.
The pair team up with Gus’s former right hand man Mike Ehrmantraut (Jonathan Banks) to use an industrial electromagnet to destroy the laptop’s content at the police holding centre. With Mike now joining the three-man operation, Walt and Jesse continue to cook as advised by Saul Goodman (Bob Odenkirk) using a pest extermination service as a cover-up for their cookouts.
Skyler’s (Anna Gunn) arrangements to pay off Ted Beneke’s (Christopher Cousins) IRS debts using the family’s illicit drug money compels Walt to cook again to earn back the $600,000 lost.
Enter Lydia Rodarte-Quayle (Laura Fraser), an executive with Madrigal Electromotive GmbH, the parent company of Gus’ fast food chain and remaining link to help the revamped blue meth business. After negotiating with Mike, she agrees to help the three business partners to acquire the necessary ingredients for the operation to continue.
Skyler learns of her husband’s return to meth production and fears for the safety of her family. She discloses to Marie of her worries and waits for Walt’s cancer to return.
When the flow of methylamine is disrupted, a key component to the production of meth, Lydia help Walt, Jesse and Mike plot a train heist carrying a large shipment of the chemical. Walt hires on another hand, Todd (Jesse Plemons), who mercilessly shoots a child passing through the scene during the heist to get rid of all witnesses.
As the investigation into Gus Fring’s death and business continues, Mike is tracked by the DEA. Both he and Jesse express their desires to leave the business, but a stubborn Walt tries to prevent their departure. He eventually takes on Todd as the new assistant cook to his lab.
However, his dealings with Mike are far from over. With Gus gone, former business associates locked away in prison find themselves in a position with valuable information in exchange for freedom. Walt fears that anyone who talks to the DEA about Gus’s ring will let out information and blow his own strategically placed cover. Walt confronts Mike to reveal the names of the men involved to have them killed, but after Mike refuses, Walt shoots and kills him.
Walt eventually acquires the names from Lydia and has all ten of the drug jail connections killed off. Lydia, now hoping to gain Walt’s trust to protect her own life, arranges for Walt’s blue meth to be shipped to the Czech Republic where she has connections with distributors.
Several months pass and business is booming. Skyler admits her fears of security to Walt, who agrees to retire from the business.
We’re left with a scene of the White household reunited once more with Hank and Marie (Betsy Brandt) over for dinner. Hank heads to the bathroom and finds a copy of Walt Whitman’s Leaves of Grass. On the inside, he discovers an inscription “To my other favorite W.W.” signed with the initials G.B. Seeing this, Hank remembers the similar inscription found on Gale Boetticher’s (David Costabile) meth production notes confiscated at the murder scene months ago. He sees that G.B. refers to the dead suspect, and that W.W. must refer to Walter White’s very own Heisenberg.