
Hank Schrader is Walt's macho, DEA agent brother-in-law. One of Hank's investigations involves the high-quality blue crystal Walt and Jesse are producing.
When the drug dealer Tuco kidnaps Walt, Hank takes a leave of absence to search for him and winds up killing Tuco in a shootout.
Hank's heroics earn him a promotion and a part-time assignment at the DEA's El Paso office, but the shootout has left him with anxiety attacks that increase in intensity after drug-cartel members ambush Hank and other El Paso agents in Mexico. Hank finally opens up to Walt, who advises Hank to face his fears and move on.
Walt and Hank generally get along, though Walt resents it when Walter Jr. seeks advice from his uncle. Walt and Hank nearly come to blows when Hank tries to prevent Walt from pouring tequila shots for his son at a party celebrating Walt's cancer remission.
The two patch things up, though, and Hank hits up his DEA-Albuquerque team for donations to Walt's cancer fund, right before Hank tells them he's sure that "Heisenberg" — the street name for the mystery man behind the blue crystal — remains at large in Albuquerque.