In "Pilot," we saw Walter White, high school chemistry teacher turned crystal meth manufacturer, use his knowledge of chemistry to escape two gun-wielding drug dealers. We saw his initial reaction of terror, followed by nausea, followed by excitement. His passion for his wife reflects his passion for life, and is a stark contrast from a few days earlier, when he wasn't interested in sex at all.
In "Cat's in the Bag...," we start at the moment the last episode ended, with Walt and his wife in bed. Then we rewind, to see exactly what happened to Walt and Jesse in the desert, in a crashed RV with two bodies in it.
The partners in crime aren't functioning at top form, or perhaps this is top form for them. Paying a tow-truck driver with chemical-soaked twenties, pledging to never see each other again, and leaving physical evidence behind in the desert: already none of these things suggest cool heads or an easy future. When one of the bodies in the back of RV starts to move, things quickly go from bad to worse.
Much of this episode played like dark comedy, with a formerly-dead drug dealer running down the street, and "Well, he did try to kill us both yesterday, so there is that," and "Best two out of three?" The comedy helps to soften the seriousness of the situation, as Walt and Jesse have to dispose of two bodies, one living and one dead.
At one point, Walt says, "We are in this 50/50, okay?" but it's hard to see how that works out. Are manufacture and distribution even remotely equal? So far, Walt fronted the cash for the RV, supplied all the lab equipment, and created the "glass grade" crystal meth, while Jesse made contact with drug dealers who tried to steal everything, one of whom, Emilio, is now dead thanks to Walt, and the other, Krazy-8, is locked in the basement. Jesse tries to lay it all at Walt's feet, but that seems to be just part and parcel with Jesse's irresponsibility. Walt may come to regret his choice of business partners, though I'm not sure other low-level dealers are any better.
Walt still hasn't told anyone about his cancer diagnosis, and he definitely hasn't told his family about his new involvement in the drug trade, so his interaction with his wife Skyler is increasingly strained. In the middle of a most joyous occasion, an ultrasound test in which they find out Skyler is expecting a daughter, her comments remind Walt that he won't live to see his daughter reach her teens, and his joy disappears. When Skyler confronts Walt about Jesse Pinkman, after using *69 and the Internet to identify him from an ill-advised phone call to Walt's home, Walt cops to the lesser offense of buying pot from Jesse, apparently hoping it will satisfy her. Instead, it leads to Skyler confronting Jesse to deliver an ultimatum, and now Jesse knows that Walt's brother-in-law is a DEA agent.