Synopsis: Unassuming high school chemistry teacher Walter White discovers he has lung cancer. Desperate to secure his family's financial future and finally free from the fear that had always inhibited him, Walt teams up with a former student to turn a used RV into a mobile drug lab.
In the New Mexico desert, a man wearing nothing but his underwear and a gas mask erratically drives an RV down a desolate dirt road. In the passenger seat, another man is passed out, also wearing a gas mask. In the back of the RV are two bodies. After crashing the RV in a ditch, the driver climbs out, dons a shirt hanging from the side view mirror, and retrieves a video camera and gunfrom the vehicle. Recording a message on the camera, the man identifies himself as Walter Whiteand bids a cryptic farewell to his wife and son. Sirens are heard in the distance. Walt walks onto the road and awaits the apparent approach of police, gun in hand.
Three weeks earlier, it is Walt's 50th birthday. Inside his modest suburban home in Albuquerque, Walt wakes up before dawn and exercises while contemplating of a plaque on his wall commemorating his contributions to research that won a Nobel Prize in Chemistry. At breakfast, his pregnant wife, Skyler, hands him a plate of eggs topped by veggie bacon spelling out "50". They banter with their son, Walt Jr., who has cerebral palsy. Afterwards, Walt drops off Junior at J. P. Wynne High School, where he also works as a chemistry teacher. In class, he explains to his apathetic students how he regards chemistry as the study of change as well as matter.
After school, Walt performs his second job at a car wash, where he finds himself wiping down the convertible of a disrespectful student. Returning home, he discovers that Skyler has organized a surprise birthday party for him. Among the guests is Walt's gregarious brother-in-law, Hank Schrader, a DEA agent. Coincidentally, Hank is the subject of a local news report covering a methamphetaminelab bust. Walt is impressed with the amount of money recovered from the dealers, and Hank discloses that he confiscated $700,000. Hank then invites Walt to accompany him on another bust as a ride-along. Meanwhile, Skyler talks to her sister Marie, Hank's wife, about her pregnancy.
While working at the car wash the following day, Walt suddenly collapses and is taken away by ambulance. At the hospital, a doctor informs a detached Walt that he has inoperable lung cancerand has a couple of more years to live at best. Upon returning to the car wash, Walt becomes angry when his boss, Bogdan, asks him to wipe down cars again. Walt makes a scene and screams obscenities at Bogdan as he storms out of the car wash.
Taking up Hank's offer, Walt accompanies him to a bust along with his partner, Steven Gomez. While Hank and Gomez raid a meth lab belonging to local dealer known as "Captain Cook", Walt waits outside in their SUV. There, he unexpectedly spots a former student named Jesse Pinkman escaping through the window of a neighboring house. As Jesse flees the scene, Walt realizes that he is the dealer whom Hank and Gomez are trying to catch. Later that night, Walt visits Jesse's house and blackmails him into letting him become a partner in his meth operation, with Walt offering his knowledge in chemistry in exchange for Jesse's knowledge in drug dealing.
The following day, Walt steals boxes full of chemistry equipment from his high school, while Jesse arranges to buy a used RV that will be used as the duo's mobile meth lab. Upon driving into the desert, Walt strips down to his underwear (so as not to contaminate his clothes with chemical odors) and cooks his first batch of methamphetamine. Jesse is astonished with the chemical purity of the product Walt has produced.
Jesse takes a sample of Walt's meth to Krazy-8, a mid-level drug distributor who happens to be the cousin of Jesse's partner, Emilio Koyama. Emilio, who was arrested in Hank's bust and is now out on bail, believes that Jesse ratted him out. The three then drive out to the RV, where Krazy-8 asks Walt if he wants to switch allegiances. Before he can answer, Emilio recognizes Walt from the bust and begins threatening him. Jesse tries to flee, but trips and knocks himself out on a rock. Walt barters for his life by promising to reveal his meth formula.
Emilio ties up Jesse, then joins Krazy-8 in watching Walt cook. As Walt prepares the ingredients, Emilio absent-mindedly throws a cigarette out the window, thereby starting a brush fire. Inside, Walt mixes chemicals that produce a deadly vapor before he dashes out of the RV. Krazy-8 and Emilio begin firing bullets through the door of the RV over Walt's head, but are eventually overcome by the fumes. Walt unties Jesse, puts a gas mask on him, and props him in the passenger seat before making his attempt to escape in the opening scene. With the sound of sirens closing in, Walt tries to shoot himself only to find that the gun's safety is on. However, he soon realizes that the sirens he is hearing are not coming from police cars, but from fire trucks responding to the brush fire. Walt hides the gun in the back of his underwear while Jesse, sporting a black eye, comes out to join him. Walt's first day as a meth cook leaves him spent, shaken, but also invigorated. Returning home, he meets Skyler's troubled queries with atypical sexual aggression which leaves her stunned.