Short Answer 
In “Breaking Bad,” Hank discovers a shocking truth about his brother-in-law, Walter White, when he finds a handwritten dedication from Gale Boetticher in a poetry book Walter gifted him. This revelation prompts Hank to reevaluate his suspicions, leading to a dramatic confrontation as he seeks answers about Walter’s double life as the drug lord Heisenberg.
Step 1: Hank’s Discovery
Hank Schrader, a character in “Breaking Bad,” uncovers a shocking truth about his brother-in-law, Walter White. This revelation occurs in Season 5, Episode 8, when Hank is casually looking through a book of poetry, specifically by Walt Whitman. The book, which Walt had gifted to Hank, becomes pivotal to the storyline and the unfolding drama between the characters.
Step 2: The Handwritten Inscription
As Hank examines the poetry book, he stumbles upon a handwritten dedication from Gale Boetticher, a character linked to the drug trade. This inscription serves as a crucial clue, prompting Hank to reconsider his previous findings about Walter. The connection between the deceased chemist and Walter helps Hank piece together evidence that ties his brother-in-law to the notorious drug lord, Heisenberg.
Step 3: The Confrontation Ahead
This moment of realization dramatically alters Hank’s perception of Walter and sets the stage for a high-stakes confrontation between the two. The intensity of their relationship escalates as Hank becomes determined to confront Walt about his double life as Heisenberg. This pivotal twist significantly impacts the storyline, contributing to the show’s dramatic tension as the series progresses.