Owen takes a special interest in a murder investigation when the victim, an airport supervisor, also turns out to be the brother of a confidential informant who was killed a few years ago. Meanwhile, Clark's newly sober mother shows up wanting to reconnect with her children, but Clark is hesitant to let her.

McKenzie catches a break in a case that's near and dear to her heart when bullets found at the scene of a subway shooting match those used to kill her brother several years ago. Meanwhile, Owen begins to have second thoughts about his impending retirement.