In the New Mexico sun, a young boy rides his motorbike through the desert. He happens upon a tarantula, and lets it crawl over his hands. The kid's no coward. Just a little curious. He puts it in a jar and heads back to the bike with his new pet. After fastening his helmet for safety, he pauses. He's heard something in the distance. Was that a whistle? He rides off to investigate…

After that context-free opening, we're in Hank's new office. He's just about done moving in, when Walt of all people shows up. He needs to talk. After Gomez leaves (to catch the real criminals, jokes the largest meth kingpin in the southwest) Walt thanks his brother-in-law for taking care of the kids. It's no problem, Hank assures him, when Walt breaks down and confesses that Skyler doesn't love him anymore, and thinks he's an unfit father. A perfect example of how the best liars tell most of the truth.

Naturally, Hank is sure he's overreacting, and that things will get better. Ill-equipped to deal with a grown man weeping, the new ASAC excuses himself to get Walt some coffee…all according to plan. Walt collects himself and attaches a device to Hank's hard drive then places a bug in the framed picture of Hank and Marie. Hank comes back before he finishes, but Walt makes it look like he was just admiring the happy couple. And you thought Gus was pretty brazen with how he pretended to support the DEA? Apparently that was playing it safe.

We don't have to wait long to see what Walt's planning. In some underground slice of hell, Mike, Jesse, and Walt handcuff an understandably (this time) frantic Lydia to a table and put a script in front of her. They're going to make a phone call, and she's going to read it, verbatim. Any deviation and Mike will take out his pistol and shoot her in the head. After having her recite the consequences for funny business—once again, that's a pistol shot to the head—they call Hank and have her ask about the tracking device she noticed on a container of methylamine. Did the DEA put it there and what should she do about it? Hank will look into it. Thanks to the bug, they get to hear the immediate fallout.

Neither Hank nor Gomez have any idea what Lydia was talking about, which means Lydia must have put it there. Law enforcement, having heard about the device, will suspect the methylamine is in danger and clear out the warehouse. Walt and Jesse will try to get to the chemicals first, while Mike takes care of Lydia, who still claims she's innocent. Jesse believes her, but Mike tells him "everyone sounds like Meryl Streep with a gun to their head." Glorious.

Just then, Hank calls another department and confirms that, in fact, they ARE responsible for placing the tracking device. There's one on every barrel. For once Mike's instincts were wrong: Lydia wasn't trying to pull one over on them. Just the opposite, she saved them. Yet this is still almost the worst case scenario. Now all the methylamine is off limits. And even though she didn't betray anyone, Mike still wants Lydia dead for putting out the hit on him. They argue more, with Jesse being the only one who cares that they'd all be in jail if it wasn't for her, while Lydia has a new offer. If they let her live, she has a way they can get all the methylamine they'll ever need.

Mike and Jesse wait outside while Walt listens to her proposal. Not sure how he got them to agree to the alone time, but never mind. Lydia asks Walt for a guarantee that she won't be killed after telling them the plan. He agrees, but that's not good enough. She wants him to swear on the lives of his children. Walt bluntly tells her she has no leverage, and that trust goes both ways. He wants to know why she put the hit out on Mike. She tells him about the guys Mike is protecting against her own interest, and considering those are the very same men Walt is forced to give hazard pay to, he likes her answer. Though of course he doesn't show it, and merely asks how much methylamine she's actually talking about. 24,000 gallons. Well then.

According to Lydia a freight train full of chemicals will pass through a three mile dead zone in New Mexico, wherein no one will be able to communicate with it. She can give them the time, place, and specific location of the methylamine on the train, and they can rob it. That's not quite the simple exchange they were hoping for. A train robbery? Even for this show, that's pretty "old west." But Lydia assumes these scary men can pull it off, and even wants a cut of the take for the informations she'll be supplying. There's it is: The greedy, entitled overreaching that explains how she could have become a criminal in the first place.

Mike points out the biggest issue. They'll have to kill the crew—an engineer and a conductor. "I have done this long enough to know that there are two kinds of heists. The kind where the guys get away with it, and the kind that leave witnesses." The ever ruthless Lydia can't believe this is a problem. They were just about to kill her, after all.

At the Schraders', Hank tries to get Holly to refer to him as ASAC, while Walt Jr. wants to be left alone. Sure, he just got a sports car, but now he's being forced to stay at his aunt and uncle's house for a few days! Poor guy. Hank even offers to watch Heat on blu-ray with him, but it does no good. Hey, isn't that the movie where criminals are brought down by a heist gone wrong because the new guy on the team  goes overboard and kills someone he wasn't supposed to? Something like that.

The three amigos (face it Saul, you've been ousted) decide what to do about the train. Mike wants to go back to a sudo cook, sans methylamine, but the profits would be a fraction of what they'd get selling the blue stuff. Walt obviously doesn't want that, and points out how this would be less of an issue if they weren't on the hook for Mike's hazard pay. This gets the two of them really fighting, leading Jesse to have another epiphany. They can solve the problem without killing anyone. Using…magnets?

A black-hatted Walt scopes out the train tracks, and sees potential. After measuring the tracks in front of a bridge, Jesse's sure it will work. With the help of the Vamanos Pest guys, they go to work, burying huge empty tanks beneath the bridge and filling some with water. Todd is curious about what, exactly, they're doing. The plan is to empty a thousand gallons of methylamine from the train and replace it with water. They'll get enough of the precursor to cook for a lifetime, while only diluting the train's contents and making it look like the supplier in China sent them a weak batch. "No one other than us can ever know that this robbery went down," Jesse tells him. "Nobody. Got it?" Todd answers in the affirmative, and Walt asks if he's sure. "Yes sir," he says, eager to impress. They thought of everything.

Walt arrives home to find Junior won't leave the house. Skyler tells him he got what he wanted, but Walt intervenes on her behalf and tells his son to go back to Hank's. Walt tells Skyler it'll all pass, but she shoots down his efforts at civility and claims she's no longer his wife, but his hostage. She accepts it, and she'll do whatever he wants as long as the kids aren't in the house. He agrees. My, what a family you've built for yourself, Walt. Skyler sees how dirty he is and asks if he's been out burying bodies. He gives a slightly more ridiculous answer. "Robbing a train."

Lyida sends them the info and just like that, it's heist time. First step, stopping the train. The best liar on Saul's payroll, Kuby (Bill Burr), parks a truck right on the tracks, forcing the freight to come to a halt over the bridge. While the engineer and conductor get out to help him, Walt, Jesse, and Todd spring into action. Jesse gets under the tracks to steal the methylamine from below, while Todd climbs onto the tank to add the water. Everything goes smoothly until the requisite hitch in the caper: A good samaritan arrives in his car and offers to push Kuby's vehicle off the tracks.

Mike tells Walt to pull the guys off the train, but he's not having it. He wants his thousand gallons. When he finally tells them they're done, the whistle's been blown and the train is about to go. Jesse and Todd seal their respective entry points on the tank with no time to spare. Jesse has to lie under the moving train, while Todd has to jump off it. Despite the close call (and more likely because of it) Walt and Jesse are ecstatic. Todd celebrates with them, finally one of the team.

Then they hear it. The humming of a motor bike. They turn to see the little boy from the opening of the episode staring at them. They all freeze, not sure what to do. He waves. Todd waves back. Jesse looks to Walt for a little guidance, but Todd takes the initiative: He pulls out his gun, steps forward, and shoots the kid square in the chest. Jesse's cries to stop him went unheard. The tarantula crawls in its jar.

And that was the point of no return. We're in the deep end now. Jesse's "never harm a child" line has been horribly crossed, and he may never be able to live with himself. Todd was an idiot—the kid obviously didn't need to die; a million lies could have worked and drawn far less attention than the murder will—but he likely wouldn't have done it had Jesse and Walt not been so adamant about there being no witnesses. What happens now is anyone's guess, but there's simply no coming back from this. The fun times are gone forever.

Follow Michael on twitter, check out his blog Story is God for more on all things fictional, or reach him at mchasin@usc.edu.