Season 3s "Fly" the first episode directed by Loopers Rian Johnson, whose "Ozymandias" might stand as the best of the series could be the most polarizing hour in Breaking Bads run. You remember it: The one where Walt, obsessed with the idea that the insect that's infiltrated the pristine confines of his superlab will contaminate the cook, spends the entire hour on an Ahabesque quest to destroy it before everything is ruined. Jesse stumbles into the middle of Walt's seemingly insane overnight pursuit "So you're chasing a fly, and in your world, I'm the idiot" ultimately finishing the fly-swatting job while an exhausted Walt, eased off the hunt by a cup of coffee Jesse dosed with sleeping pills, naps.
Oh, right, there are some other things going on: Walt's discovery that Jesse is skimming product, an offense that could get him killed by Gus; Walt's admission that he met Jane's father the night Jane died; Walt's frustration at his inability to explain the motives for his cooking to Skyler; the crushing guilt (Walt is still capable of experiencing guilt) of his calculating non-intervention in Jane's death. When Walt pressurized the lab, he wasn't messing around. By the end of it, you feel like they've been locked in a phone booth, not in the cavernous meth-fabricating palace Fring built them.
So dismiss this as a boring bottle episode if you must. There are no magnets, no train heists, no fatal standoffs in the desert. It's just two people chasing a fly.