“Blood Money” is the root of it all in “Breaking Bad” Episode 509. But what’s really behind the “Heisenberg Principle?”

Peter Gould, one of the show’s co-executive producers, says much of the “Breaking Bad” storyline comes to fruition with Episode 509. He says the characters “Walter” and “Hank” finally square off in a very pivotal scene.

“It’s violent physically and it’s violent emotionally,” he said. “All hell breaks loose.”

Up until now, DEA agent, “Hank Schrader” was blissfully unaware of his brother-in-law’s secret activities. He finds a copy of a book with the initials “W.W.” atop one of the pages. Believing the initials stand for “Walter White,” the agent works feverishly to confirm his sister’s husband is, in fact, the infamous drug dealer known as “Heisenberg.” The production crew said the scene between the characters was volatile and potentially injurious. They wanted to take extra precaution to protect the two actors.

“We had special mats that look like cement,” said Breaking Bad’s stunt coordinator Laurence Chavez. “We also considered using stunt doubles.”

Bryan Cranston, who plays the lead role as “Walter White,” also directed this ninth installment of Season 5. He says the physical demands did not only extend to directing.

“You ‘snap’ your neck to receive a hit,” he said. “You do that enough times, by the time you get home, you’re sore.”

Co-executive producer, Melissa Bernstein says she believes part of the show’s attraction is its staunch realism. She says the crew works especially hard to preserve visual integrity. If a character is injured their physical appearance should be true-to-form.

“Make-up artists add blood and discoloration,” she said. “A wound should look real-world appropriate two minutes afterward.”

While, anticipation about Breaking Bad’s final season seems to be reaching a fever-pitch, Bernstein says TV viewers should keep a watchful eye. She says Episode 509 is laying the groundwork for the final end.

“This is ending for the series,” she said. “The audience needs to stay tuned in.”