Frank learns that one of his most highly-decorated officers, a German Shepard in the K9 unit by the name of Bosco, is being accused of police brutality by Preston Ellis, the father of a young boy whom he claims was attacked by Bosco. The media amps up the rhetoric on the story and there is a strong public outcry for Bosco to be put down, but after meeting Bosco and his handler, Denise Donohue, Frank is convinced that Bosco might be innocent after all. He has a team of investigators look into the matter, and they discover that Ellis framed Bosco for an attack that another dog committed. Meanwhile, Danny and Baez investigate a homicide in which Baez' own estranged brother, a former drug addict named Javi, is the lead suspect. When Baez and Danny discover Javi near death in his apartment after a staged drug overdose, it becomes clear that the original murder victim was an innocent bystander and that Javi was the intended target of a hit put out by Benny Russo, a slippery drug dealer who manages to evade every drug charge thrown his way. Using Javi as bait, Danny and Baez stage a sting to nab Benny, who nearly throws Javi into a wood chipper before they arrive to save him. Henry also stages an investigation of his own when he begins to suspect that Colleen, his former partner and widow of his old NYPD pal, may have had a hand in her husband's death.