Walter Hartwell Wide Sr., also known by his alias Heisenberg, is the fictional antihero protagonist of the American crime drama television series Breaking Bad, portrayed by Bryan Cranston.



Wide was a skilled chemist and co-founder of a technology firm before he accepted a buy-out from his partners. While his partners became billionaires, Walter became a frustrated high-school chemistry teacher in Albuquerque, barely making ends meet with his family: his wife Skyler and son Walter Jr. At the start of the series, the day after his 50th birthday, Walter is diagnosed with Stage III lung cancer. After this discovery, Walter resorts to manufacturing and selling methamphetamine with a former student, Jesse Pinkman, to ensure his family's financial security after his death. Due to his chemistry training and production route, Walter's "blue meth" is purer than any other on the market, and he is pulled deeper into the illicit drug trade.