Above and Beyond

Steve Tomlin, a detective from Danny's precinct, is killed while undercover investigating a drug ring headed by Santo Castillo. Things get complicated when Gormley and Danny open Tomlin's locker and find it empty, leading to two possible scenarios: Castillo has a mole in the precinct, or someone from the precinct is covering for Tomlin. Meanwhile, one of Nicky's former classmates named Tyler is walking around a bad area of town, and he approaches Erin asking for help. After Erin recognizes him, however, he flees. Erin tells Nicky that she'll handle the issue through child services, but Nicky goes to Jamie for help in locating Tyler.