Heroin addict Mark Renton stumbles through bad ideas and sobriety attempts with his unreliable friends -- Sick Boy, Begbie, Spud and Tommy. He also has an underage girlfriend, Diane, along for the ride. After cleaning up and moving from Edinburgh to London, Mark finds he can't escape the life he left behind when Begbie shows up at his front door on the lam, and a scheming Sick Boy follows.

Walt must deal with the chain reaction of his choice, as he and Jesse face new and severe consequences. When danger and suspicion around Walt escalate, he is pushed to new levels of desperation. Just how much higher will the stakes rise? How far is Walt willing to go to ensure his family's security? Will his grand plan spiral out of control?

Walt is faced with the prospect of moving on in a world without his enemy. As the pressure of a criminal life starts to build, Skyler struggles to keep Walt’s terrible secrets. Facing resistance from sometime adversary and former Fring lieutenant Mike, Walt tries to keep his world from falling apart even as his DEA Agent brother in law, Hank, finds numerous leads that could blaze a path straight to Walt. 

Season three shifts its focus to Pablo Escobar’s real-life successors in the drug trade: Colombia’s Cali Cartel, "the biggest drug lords you’ve probably never heard of."