[WARNING: The following story contains spoilers from Monday's episode of Better Call Saul. Read at your own risk.]

Better Call Saul has spent most of its early episodes sketching in the history of the man who would one day become Saul Goodman. But on Monday's episode, theBreaking Bad prequel decided to devote the entire episode digging into the (tragic) past of Mike Ehrmantraut.

The episode began with Mike (Jonathan Banks) arriving in Albuquerque — with a bullet in his shoulder — in an attempt to mend fences with his daughter-in-law Stacey (Kerry Condon). During the course of their strained conversation, it became clear why Mike had finally left Philly behind: He was mourning the death of his son.

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Fortunately for Banks, the backstory Saul co-creators Vince Gilligan and Peter Gould dreamed up for Mike was in keeping with what he had already imagined. "We're in accord," Banks tells TVGuide.com. "[On Breaking Bad,] when I took the Mylar balloons and gave them to my granddaughter and then go shoot people, I tell her, 'Your mom is waiting. Go on to your mom.' Vince directed that episode, and I said to him, 'That's my granddaughter; [her mom] is not my daughter. Whatever's happened to Mike has happened because of his son.'"

Indeed, the loss of Mike's son was a transforming experience for Mike — one he was forced to relive when two Philadelphia cops knocked on Mike's door at the end of the previous episode. And even though Mike wouldn't talk to his former colleagues without a lawyer — enter Mr. Jimmy McGill (Bob Odenkirk) in his best Matlocksuit --Mike quickly turns his interrogation to his advantage and gets some much-needed intel. It turns out, the Philly cops are looking into the murder of two other officers who were involved in the ambush that got Mike's son killed.

Although Mike ultimately satisfies the investigators' queries, the case doesn't die there. Instead, Mike confronts Stacey for calling the cops in the first place. When she explains she did so because she feared Matt was a dirty cop, Mike goes ballistic. However, after he calms down, Mike finally tells Stacey the truth in heartbreaking fashion. Turns out, Matt died because Mike wouldn't let his son turn his partners in for skimming money. In fact, Mike, who was also on the take, convinced his straight-arrow son to take the money as well to keep from arousing suspicion. Unfortunately, Matt's partners still didn't trust him, and arranged the ambush to cover up Matt's murder. "I broke my boy," Mike says fighting back tears.

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"His son was murdered in large part because of him," Banks says. "That's the way he feels. The son looked up to his father, and Mike says it in the monologue, 'He had me on a pedestal.' Mike's not the kind of guy who would feel like he deserved to be on a pedestal. I think he was glad that his son thought that, and it was one of the most important things in his life. And he let his son down. How heavy is that guilt? He lost his soul because of it. He lost his life because of it. He is the walking dead."

More flashbacks showed that Mike drowned his guilt with booze until he finally figured out how to prove Matt's partners murdered him. And once he tricked them into confessing, Mike killed both of them, taking a bullet to the shoulder for his troubles. And even though Mike is now having to answer questions about those cops' deaths, Banks believes Mike feels completely justified for taking the law into his own hands. "If he could kill them all over again, he'd kill 'em twice. Maybe three times" Banks says. "There's no reason for him to feel like he should be incarcerated for their deaths."

Even though Mike might have taken solace in the deaths of his son's killers, Banks says what really pulled Mike through his grief was his granddaughter, who became a focal point for the character on Breaking Bad. "He is [only] alive and maintaining because his granddaughter is a part of his son," Banks says. "[She's] the only decent thing left in his life. And he owes his daughter-in-law. He helped take her husband away. He needs to take care of her, he needs to watch out for her. He owes her."

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Now that viewers have gotten to understand more about what made Mike the man he is, the show can continue to develop his growing relationship with Jimmy. But even though Jimmy helped Mike out of a jam, don't expect them to automatically partner up. "Jimmy's irritating, but I think Mike's also amused by him," Banks says. "If you said to Mike, 'You know, you're gonna end up working with this guy,' he would be a little surprised by that."

Speaking of surprises, many viewers might have anticipated seeing Mike in action sooner this season. Instead, most of his screen time has come while Mike was sitting in the toll booth at the courthouse, where he constantly harasses Jimmy about not having enough stickers to validate his parking. Even so, Banks says never doubted his choice to return to Better Call Saul .

"There were footnotes in the script that said, 'Hold on, Mike's coming,'" Banks says with a laugh. "I trust my writers, and I love playing the character. It was great to go back and do the character."

Better Call Saul airs Mondays at 10/9c on AMC. What did you think of Mike's backstory?