The showdown between Walter and Gus takes center stage for this story, and just one or two subplots manage to nose their way in. The resolution of the season-long conflict was mostly satisfying. Mostly.
First, a fond farewell to Giancarlo Esposito, whose dead-eyed Gus Fring will be missed. The show has done a good job of giving us progressively better villains -- from Krazy-8 to Tuco to the cousins to Gus -- and Mr. Esposito will be a hard act to follow. (Hey, we may well get more ... the many dead characters on this show tend to have flashback-related half-lives.) Season 5 will have some big shoes to fill coming up with a new villain. And they'll have a hard time topping the lastest in a series of over-the-top deaths. Thumbs-up for not relying entirely on the CGI to carry that scene; little touches like Gus straightening his tie (which I buy) and the shocked reaction from the nurses who know this patient is beyond help ... such touches make the scene.
Jesse Pinkman didn't have a whole lot to do this episode: just some adroit cat-and-mouse with police detectives followed by playing the damsel-in-distress at the superlab. (Ironically, having proven that he can cook nearly as well as Walter, he was treated to the very fate that Walter had avoided, twice: being essentially a prisoner/slave of drug lords.) He got a happy ending with his nearly-family, which I didn't see coming.
The family at Camp Schrader ... well, they might as well have had the week off for all the impact they had on the story.
So that leaves Walter as the almost full focus of the episode, following a plan of action he formed an episode back when his spinning pistol pointed to the Lily of the Valley potted plant, and continuing a character transformation that began in that same exact spot, tossing lit matches into his pool before resolving to cook methamphetamine. (What IS it about that pool?) His list of crimes now includes sending the nice neighbor lady into harm's way to see if he could enter his house safely, bombing an old folk's home, and killing two henchmen in cold blood. Oh, and poisoning a child to manipulate his estranged partner.
Wait, what was that? Yeah, it looks like he poisoned Brock. How, exactly? When did he get the opportunity? And HOW did he get that ricin cigarette away from Jesse? Did Saul Goodman's goon swap packs with Jesse during his patdown? (Looking at it frame-by-frame, no, he didn't.) And if so, then that means that Saul and Walter conspired in it ... so how come Walter has to go to such lengths to track down Saul early in the episode? There are holes here; I doubt they'll be filled, but, rather, papered-over early in Season 5.
Unusually, things feel mostly resolved at the end of this season. There's no dangerous villain, no impending death, no exploding planes ... no immediate crisis of any sort. The story could move in many directions. It seems unlikely that Walter will retire (he tried that before in Season 2's "Over," and it didn't take). Once again, the field is clear for expansion of the business (with Gus AND the bulk of the Cartel dead). But the nature here is different from previous stories; in the deaths of Emilio, Krazy-8 and Tuco, Walter and Jesse essentially bumbled their way into success. This time, the take-down is big, the execution was cold-blooded calculation, and the hole in the local drug trade is bigger than ever. There are repurcussions coming -- locally from the DEA, and from the remaining Cartels in Mexico ... and Mike, who Jesse says is "gonne be pissed" -- but Walter has grown to the point that he is up to the challenge.
And that's Walter, as in Walter alone. Previously, he had relied on his Heisenberg persona to do his dirty work. Not now. At the end of the episode, Walter calls Skyler and tells her that all is well with a two-word phrase: "I won." Walter White and Heisenberg are two very distinct characters as played by Bryan Cranston, and I honestly cannot discern, in that final line, which character said those words. The two have become one. Metastasization complete.