1. The Book (Season Five, Episode Eight: "Gliding Over All")
The final scene of the Season 5A may very well be the lowest of all lows for Walt. At the White homestead, Hank, looking for something to read, finds a copy of Leaves of Grass. This is, of course, the book Gale gave to Walt, inscribed, "To my other favorite W.W. It's an honor working with you. Fondly, G.B." A flashback brings us to the scene where Hank asks Walt to assist with Gale's murder case: Hank shows Walt a notebook inscribed "To W.W," joking how those are his initials, too. Walt, laughing, replys, "You got me!" Hank, now out of the flashback, realizes that Walt is Heisenberg, and his reaction is one of awe, outrage and sorrow. This is the piece that could complete the puzzle that is Breaking Bad – such a careless, foolish mistake shows just how low Walt has sunk. There's also some irony in the fact that Walt's downfall is brought on by a book in his home, as it was his desire to protect that space – and everything inside of it – that made him first "break bad."