A boy on a dirt bike zips through the desert, pausing to marvel at a tarantula. As it crawls across his hand, he hears a train whistle in the distance. He puts the tarantula in a glass jar, jumps back on his bike and zooms off.
Hank is settling into his new office, following his promotion to ASAC, when Walt stops by. Walt thanks Hank for taking the kids, then breaks down and tearfully confides that Skyler doesn't love him any more. Uncomfortable with this upwelling of emotion, Hank closes the office blinds and offers to fetch them both some coffee. As soon as Hank exits the room, Walt springs into action. He pulls open a framed photo of Hank and Marie, and plants a tiny electronic listening device inside. As Hank walks back in, Walt hurries to reassemble the frame. "You two are so great together," Walt tells Hank, still holding the photo and feigning a nearly tearful state.
Mike, Walt, and Jesse kidnap Lydia and bring her to an abandoned warehouse, where they handcuff her to a table. At Mike's orders, she calls Hank to report that she spotted what looked like a GPS device on one of Madrigal's methylamine barrels, and to ask how she should handle that development. On a laptop, Jesse taps into the bug Walt planted in Hank's office, and they all listen as Hank and Gomez puzzle over who planted the GPS device - supporting Mike's belief that it was Lydia who did.
As Lydia protests her innocence, Hank calls the Houston DEA office and learns that his colleagues in Texas did indeed tag the methylamine barrels - not just the one that Lydia spotted, but all of them. Still, Mike maintains they should kill Lydia. "She's a loose cannon," he says. "The woman put a hit out on me." Besides, her barrels of methylamine are now all useless to them. Desperate, Lydia blurts out that she can direct them to "an ocean" of methylamine.
Walt talks one-on-one with Lydia, who demands a guarantee that she won’t be killed once she reveals the methylamine source. When Walt asks why she went after Mike, she says she couldn't abide his decision to pay off - rather than kill - his nine men in prison, a complaint Walt definitely shares. She asks him to swear on his children's lives that she won't be harmed, then reveals how Walt can obtain 24,000 gallons of methylamine.
Once Walt brings Mike and Jesse back into the warehouse, Lydia lays down a map revealing the route for a train carrying a tanker car full of methylamine. She zeroes in on a three-mile stretch of "dark territory" - a dead zone for all lines of communication - and suggests they rob the train there. Mike points out that in order to get away with the robbery, they'll have to kill the innocent train crew, which deeply troubles Jesse. Stymied, the guys head back to Albuquerque.
At the Schrader residence, Hank and Marie play with Baby Holly and discuss Walter, Jr.'s sullen behavior. Junior briefly emerges to grab a soda from the kitchen, but retreats back to his guest room with a snide comment: he's clearly not thrilled to be living in exile.
At Jesse's house, Mike advocates foregoing methylamine altogether and scrounging cold pills again. Walt argues that they would have to take a loss on their new equipment and a pseudo cook would drastically reduce their output, darkly reminding him that they have to keep cooking to cover the hazard pay for Mike's men. As the two bicker, Jesse speaks up: "What if we can rip off that train and no one ever knows it got robbed?"
Starting from the crossroads of train tracks, Walt, Jesse and Mike measure a span of railroad track with a surveyor's wheel. Jesse reads out distances as they walk, then stops at a low trestle bridge. "We do it here," he declares.
Later, a bulldozer digs a shallow pit under the trestle into which two large and empty containers are lowered. As Walt smoothes dirt over the freshly-buried containers, Todd from Vamonos Pest arrives with a water truck.
As Todd fills one of the containers, Jesse and Walt explain their plan to siphon the train's methylamine tank and refill it with water so that the cargo will weigh the same at both the train's origin and terminus. The batch will be only slightly diluted, Walt says, which Madrigal will blame on the supplier in China.
Walter, Jr. has returned home against his mother's wishes, and Skyler unsuccessfully tries to coax him out of his room. When Walt arrives, Walter, Jr. demands to know why he's being forced to stay at his aunt and uncle's house. Walt lays down the law, and an embittered Junior dutifully obeys his father and heads out.
Walt expects Skyler to thank him for holding the line with Junior and kicking him out, but instead she coldly reiterates that as long as Walt is in the drug business, the kids must never return. "You agree to that, and I will be whatever kind of partner you want me to be," she says. Wryly noting Walt's dirty pants, Skyler asks, "Out burying bodies?"
"Robbing a train," Walt cooly replies.
The next day, Walt, Jesse and Todd wait by the trestle bridge. With a hidden Mike standing guard nearby, Saul's henchman Kuby parks a dump truck directly on the train tracks at the crossroads, pretending the truck has broken down. The train is forced to stop. With Kuby distracting the train crew, our guys jump into action beneath the trestle bridge. As Todd climbs to the top of the tanker with the water hose, Jesse siphons methylamine out the bottom.
Back at the crossroads, a "Good Samaritan" arrives and offers to push Kuby's truck off the tracks. Mike alerts Walt to abort, but Walt refuses and insists that Jesse and Todd keep going until they've obtained the targeted 1,000 gallons of methylamine. Just as they finish, the train starts moving again. Todd jumps down from the side of the tanker car, but Jesse is forced to lay flat as the train rolls right over him.
The heist a success, the three begin cheering. The noise dies down as Walt turns off the water pump, allowing the guys to become aware of the purr of a small engine. It's the boy on his motorized dirt bike, idling nearby. The boy waves at them. Todd waves back, then immediately pulls out a gun. Jesse cries out to stop him, but it's too late: Todd fires.
The boy topples off the bike and falls to the ground, his glass jar rolling out beside him. As the boy lies motionless in the sand, the trapped tarantula claws at the walls of its cage.