Mike Ehrmantraut has been tangling with the Salamanca cartel led by Hector Salamanca (Mark Margolis). Nacho, worried that his life is in danger, approaches Mike to assassinate Tuco Salamanca (Raymond Cruz), the violent, meth-addicted drug dealer Walter White (Bryan Cranston) eventually kills in Season 2 of "Breaking Bad." Mike isn't yet a conscienceless killer and proposes getting the cartel member arrested instead. He goads Tuco into an episode of road rage and it works. Tuco then catches a case for an unlicensed firearm.
Hector begins to threaten Mike's granddaughter, forcing his hand, and Mike resolves to kill the cartel boss. Having engineered a situation where he'll have a clear shot from a sniper rifle in the middle of nowhere, that's where we find Mike in the Season 2 finale. Mike purchases a high-powered sniper rifle from Lawson, the gun dealer played by Jim Beaver who first appeared in "Breaking Bad," and heads out to do the dirty deed. He sets up his sniper nest on a ridge overlooking the Salamancas' hideout.
The Salamanca crew is busy executing Ximenez (Manuel Uriza), the drug trafficker Mike robbed in the previous episode to lure them out there, and Mike waits for his shot. Hector is there, and his goons execute Ximenez with a gunshot to the head, but Mike can't get a clear shot because Nacho is blocking his line of sight.
As he realizes he's missed his opportunity, Mike's car alarm begins to blare, and he goes back to the vehicle with a revolver drawn. But when he gets back to the wagon, there's no one in sight, with only a note stuck under his wipers with a single word: "DON'T." It's an ominous portent that a new player has entered the drug wars.
