S4E13 · Face Off

Complete story — includes the ending

Detectives question Jesse about Brock, but Saul intervenes. Afterward, Walt, Jesse, and Saul realize that Gus may be vulnerable via his visits to Hector at the nursing home. Walt visits Hector, who readily agrees to his plan. Jesse is kidnapped from the hospital and held at gunpoint in the lab, forced to cook. Following Walt's plan, Hector asks to speak with the DEA. Believing that Hector is planning to be an informant, Gus visits Hector to personally assassinate him. After Gus admonishes Hector for his supposed cowardice, Hector detonates Walt's bomb, which is strapped underneath his wheelchair; the explosion kills Gus, Tyrus, and himself. Once Gus' death is confirmed, Walt rescues Jesse, and together they destroy the lab. Back at the hospital, Jesse tells Walt that Brock is recovering and that his illness was not caused by ricin, but rather toxic berries from a lily of the valley plant. Still, the two agree that Gus needed to be killed. Skyler calls Walt after seeing news about the nursing home explosion, and he declares to Skyler that he "won". The season ends with a shot of a potted lily of the valley plant in Walt's backyard, revealing that Walt had indeed poisoned Brock.