John and Ben are the first responders to a gruesome triple homicide in Hancock Park, where a mother is bludgeoned to death and her young daughters are found bound, gagged, raped and dead in their bedrooms. In investigating the case, Lydia and Rene realize they have two very different investigation styles. Meanwhile, Sammy continues to have problems with his wife and Ben confronts John about his increasing reliance on pain pills.

Lydia and Rene are called to Compton to investigate the murder of a young SULA student, only to discover that the girl was not exactly who her parents claimed she was. Meanwhile, John takes Ben with him to Indian Wells to attend the funeral of his friend, a cop who committed suicide. On the way back, they stop at the rehab center to check in on Dewey.

After two men murder a man in a crowded nightclub, Nate discovers his daughter was an eyewitness. Meanwhile, tensions rise between Sal and Gil on the gang task force, and Sammy confronts his wife, Tammi, after discovering she has been photographing gang members.