Heroin has been smuggled into Dallas packaged as legitimate medicine, and is mistakenly prescribed by a nurse and friend of Walker's to a small child. What Walker doesn't know is that he is dealing with an old enemy.

Years ago, Walker broke up a drug cartel headed by two brothers - Carlos and Ramon Vega Garcia. Now the two men are free, and have spent the past few years in Mexico rebuilding their operation. And these brothers have big dreams - of wealth, of power, and of revenge against the Texas Ranger who once struck them down. But Walker has his own dream - of putting this brutal cartel out of business for good...