4x1: Box Cutter
Gus takes both Walter and Jesse as prisoners in the lab. Moreover, Skyler starts looking for any clues about his husband vanishing
Box Cutter starts season 4 of Breaking Bad. As we remember, the previous season ended with Jesse shooting Gale down because of the danger of this man knowing Heisenberg's recipe, and that moment is where the action starts. Jesse is profoundly shocked and goes back to his car, when Victor captures him.
Later, they go to the superlab to meet Mike, Walt and Gus, who threatens Walt and Jesse with a box cutter. Walt tries to stop Fring by telling him that if he kills him or Jesse will get nothing good for his business. So, Gus walks towards them, but suddenly, cuts Victor's throat and orders the cooking to continue.
Curious facts: Probably, the cutter that has big protagonism in this episode was the same that appears in the opening flashback scene. On the other hand, the clock that's in the Gale's neighbour house marks 10:13, a number of great relevance in another series where Vince Gillian worked, The X-Files.