An investigation is opened after Ben, John, and Officer Chickie Brown encounter an infant crawling down the street. Lydia takes a personal interest in the case after Child Protective Services gets involved, and goes out on a limb for the mother. Meanwhile, Sammy and Nate are furious when they learn their teenage eyewitness won't get police protection due to lack of funds, and put up their own money after an attempt is made on her life.

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.

Ben has a confrontation with his mother’s rapist after the man is released from prison and is devastated when his mom reveals some information she's been keeping secret for years. Meanwhile, Lydia and Josie continue to bump heads, and Sammy deals with his wife’s betrayal.

When a rape victim hires a lawyer and refuses to talk with the two detectives unless her lawyer is present, Lydia and Josie want to know why. Meanwhile, John strikes up an unlikely friendship with a boy who returned home after a sleepover, only to discover his parents had packed up and moved during the night, abandoning him and leaving him to fend for himself, Later on, John begins to feel the stress over the prospect of testifying at his father's upcoming parole board hearing, but he doesn't realize his testifying will open up an emotional can of worms that he's not prepared for.

Things are gonna change with Joel Rucker as the new captain. Lydia and Ruben investigate a convenience store murder, and Lydia uses her typical compassionate charm to collect facts on her suspect from an unassuming grandmother. Meanwhile, John and Jessica get to test their physical abilities when they're attacked on the street. Elsewhere, Sammy and Ben ride with a mistake-prone officer, but Ben is the one making mistakes... mistakes that earn him some notoriety.

Jessica goes the extra mile to assist a homeless war vet obtain an ID so he can be admitted into a shelter . Meanwhile, Sammy is determined to save a dog after he accidentally shoots it in the leg. Elsewhere, Lydia struggles with a serious personal matter while she and Ruben investigate the murder of a man who sheltered and aided women in need.