This episode’s cold open was all about the hat. That black porkpie is as important to Walt becoming Heisenberg as the rumpled fedora is to Henry Jones Jr. becoming Indy. It’s not just a hat, it’s Walt’s super-villain costume. When we first see it sitting inside Walt’s previously wrecked Aztec, it’s shot as an object of mythic power, in close-up from a low angle. And with that power returned to him, Walt starts off this episode in full pimp mode. There’s no way the great Heisenberg can be content with a boring old Aztec that, with a little love, could make it another 200,000 miles. So Walt sells it to a friendly mechanic for a measly fifty bucks and leases a pair of high-roller cars for Junior and himself.

Once back home, there’s no way Skyler can order the vehicles returned like she did the last time Walt bought a hot-rod for Junior. No, at this point Walt’s going to do what Walt’s going to do. Skyler can only hope to protect her family as best she can — a feeling not too dissimilar from the ones that came over Walt way back when he was first diagnosed with cancer a year ago. So while “Fifty-One” begins with Walt overflowing with hubris, it ends with his children being ripped away from him, as Skyler has arranged for them to live with Hank and Marie for at least a few days and maybe longer. The scene where Walt and Skyler tear into each other over this decision is the dramatic centerpiece to an episode that deals almost entirely with Walt’s home life, and it’s an excellent showcase for Bryan Cranston and Anna Gunn, who both do exceptional work through the whole hour.

“You’re back at it,” Skyler confirms early on, knowing damn well how Walt paid for the flashy cars in the driveway.

“We have to make up the $600,000 we lost,” Walt replies, not specifically blaming Skyler for the lack of cash, even though you know he was thinking it.

Skyler broaches the subject of sending Junior to a boarding school in Arizona, despite the fact that he’s about to enter his senior year of high school. “A new environment might be good for him,” she argues.

“What does that mean?” Walt asks, his eyes narrowing. “What’s wrong with their environment?”

Things get worse from there, as Walt’s dreary 51st birthday pool party — one filled with fake smiles and forced conversation — concludes with Skyler walking fully clothed into the family swimming pool and sinking down into the deep end, seemingly with no intention of resurfacing. A suicide attempt? Some kind of depression-instigated trance? Whatever it is, it’s clear that Skyler has reached her breaking point. Walt thanks Hank and Marie for recommending their therapist, but when Marie offers to take Junior and Holly off their hands, Walt quickly susses out that it was Skyler’s idea. “Voilà, the kids are out of this environment,” he barks at her once they’re alone, throwing that last word back at her. “What a coincidence.” Things continue to devolve, with Walt and Skyler eventually tossing so many threats at each other that it turns into a nasty game of one-upsmanship.

“I will not have my children living in a house where dealing drugs and hurting people and killing people is shrugged off as ‘shit happens,'” Skyler tells him, adding that she’ll hurt herself if it’ll help keep her kids away. Walt doesn’t back down, warning that he’ll have Skyler committed. Skyler says she’ll pick up some bruises and cry spousal abuse. And oh my god how this marriage has crumbled completely to the ground in only a year. By the end of the fight, it’s clear that Skyler considers her own soul lost to Walt’s new life. She tellingly identifies the meth trade as “our business” at one point, and once Walt starts pointing out the deficiencies in her various threats, she concedes that there’s nothing much she can do about her situation except wait for Walt’s cancer to return. It’s a hugely emotional and powerful moment — one rooted in everything we’ve learned about these two people over four-plus seasons — and it overshadows nearly everything else that happens in this episode.

Lydia is back this week. She’s a frazzled mess what with Hank and Gomez showing up at Madrigal to take a warehouse worker into custody. She also may have bugged her own canister of methylamine that was marked to be lugged back to Albuquerque (and then “discovered” the bug with Jesse). This doesn’t sit well with Mike, who suspects her of playing games and decides it’s time for her to disappear. Jesse, who again isn’t given much to do this week (sigh), intervenes on her behalf.

Meanwhile, Hank’s busy being an awesome detective (he notices Lydia’s mismatched shoes) and working the Fring case from all angles when he’s suddenly offered the top position at his DEA office. He accepts, which means he’ll need to turn over all field work to his underlings. Can’t imagine that lasting long with the mysterious Heisenberg still under his skin. We also learn that the DEA is putting a surveillance team on Mike. That can’t be good.

One of the reasons Breaking Bad is TV’s best drama is how effectively the show uses quick little audio and video flourishes. “Fifty-One” has the stream of blood dripping down off Walt’s newly shaved head, the loose string on the porkpie hat and the ticking watch that closes out the episode — indelible and important images all.

I can’t seem to decide what the episode’s most amusing line was: Mike’s “That’s what I get for being sexist” remark when he concludes Lydia shouldn’t have been spared or Lydia’s aside that Jesse could be “one of those undercover people they send into high schools.” Tough call.