Walter Hartwell White (also known by his clandestine alias Heisenberg) (played by Bryan Cranston) is an underachieving Albuquerque, New Mexico high school chemistry teacher who, after being diagnosed with lung cancer, starts manufacturing methamphetamine to provide for his family upon his death. Knowing nothing about the drug trade, he enlists the aid of his former student, Jesse Pinkman, to sell the meth he produces. Walt's scientific knowledge and dedication to quality lead him to produce crystal meth that is purer and more potent than any competitors'. To avoid the tedious collection of pseudoephedrine required for production, Walt devises an alternative chemical process utilizing methylamine, giving his product a distinctive blue color. His crystal meth, which is given the street name "Blue Sky," dominates the market, leading to confrontations with established drug makers and dealers.
Walt is initially squeamish about the use of violence, but gradually comes to see it as a necessity. He also comes to find his new status as a drug lord psychologically rewarding, leading him to become less and less reluctant to resort to criminal acts such as theft, extortion, money laundering, depraved indifference, and murder. Walt's descent, Macbeth-like, into the criminal underworld unearths immense levels of deeply repressed ambition, rage, resentment, vanity, and an increasing ruthlessness which alienates him from his family and colleagues.
Skyler White (née Lambert) (played by Anna Gunn) is Walter's wife. She has had several meager sources of income: writing short stories, selling items on eBay, working as a bookkeeper, and ultimately helping her husband launder money. Skyler and Walter have a son, Walter Jr., and an infant daughter, Holly. Skyler cares for Walter very much, but their marriage becomes increasingly strained due to his unexplained absences and bizarre behavior, ultimately leading to their separation. Later, once Walter reveals his operation, she aids him in laundering his funds. They buy the car wash where Walter had recently moonlighted. Although she helps Walter, she remains displeased with the situation overall. As Walter slowly becomes more of a "hardened criminal," her emotions of fear and worry for him become increasingly prevalent. When in the episode "Buried," Hank tells Skyler he is on to Walt, but needs her help to provide sufficient evidence to build a successful case, Skyler replies that she needs a lawyer and later tells Walt they should remain quiet.
Jesse Bruce Pinkman (played by Aaron Paul) is a small-time methamphetamine user, manufacturer, and dealer. In high school, he was an indifferent student in Walter White's chemistry class. Now in his mid-20s, Jesse is Walt's business partner in the meth trade. Jesse is impulsive, hedonistic, and uneducated beyond high school, but he is financially ambitious and streetwise. He talks in playful slang, likes to wear garish clothing that follows the latest trends in youth culture, plays video games, listens to rap and rock music, takes recreational drugs, and drives cars outfitted with gadgets to make them "bounce". Walt treats Jesse like a foolish son in constant need of stern correction. Jesse's own family kicked him out of their house because of his drug use. Despite the friction between them, he and Walt have a deep bond of loyalty. As a result of his relationship with Walt, Jesse becomes an excellent meth cook, ultimately leading to his exploitation by others. Despite his criminal lifestyle, Jesse is far more conscientious than Walt. He is horrified, particularly during later seasons, by the brutality at the higher levels of the drug trade, but remains involved with Walt because he's not sure what else he can do. He is very protective of children: his desire to keep children out of the violent drug world gives rise to several key events throughout the series. He wrestles with feelings of guilt about the deaths, all drug-related, of people he has been associated with. Towards the end of the fifth season he is overwhelmed by guilt and his "blood money." Jesse sees all of the pain he caused for that one duffel bag of money causing him to throw it out his car window and attempt to give it to people in need, or people who have a tie to him.
Henry R. "Hank" Schrader (played by Dean Norris) is Walt and Skyler's brother-in-law and Marie's husband, who works as a U.S. Drug Enforcement Administration agent. He is involved in investigating a meth dealer known as "Heisenberg," unaware for over a year that his prey is actually Walter. Hank has a cavalier exterior, but in reality the dark side of his job affects him more than he cares to admit. In the course of his work, Hank is promoted to El Paso, Texas from Albuquerque for a short time but experiences a traumatic event and moves back to Albuquerque. Despite his brashness, Hank is highly competent at his job and cares deeply about his family. Hank is eventually promoted to Assistant Special Agent in Charge of the D.E.A. in Albuquerque but is still determined to solve the "Heisenberg" case, which ultimately leads to his demise.
Marie Schrader (née Lambert) (played by Betsy Brandt) is Skyler's sister, Hank's wife, and Walt's sister-in-law. Marie works as a radiologic technologist. She doesn't hesitate to offer advice to others, but often fails to practice what she preaches. She shoplifts compulsively—apparently a manifest symptom of kleptomania—a behavior for which she sees a therapist. She appears self-centered and shallow, but is very devoted to her husband and cares deeply for her sister's family. Nearly all of her household and clothing items are shades of the color purple.
In Season 3, Marie becomes a major source of comfort and support to her husband, when The Cousins shoot and nearly kill Hank. With Walt and Skyler's help, she arranges for Hank to undergo an aggressive physical therapy program that is not covered by their insurance. When Hank stubbornly decides to stay at the hospital, claiming he is completely disabled, she refuses to give up on him and masturbates him to prove he still has feeling below the waist. When he returns home, however, Hank is cold and brash to Marie, despite her attempts to make him comfortable, and she spirals back into kleptomania. Once Hank begins making progress with the case, his relationship with Marie improves again. When Walt and Skyler begin to have marital problems, she volunteers to take in their children for a couple of days while they work things out.