A soulless killer is stalking Los Angeles in the second half of the hit TNT series "Major Crimes" season 4.

According to CarterMatt, the five-part story titled "Hindsight" will kick off with the Los Angeles Police Department (LAPD) facing a crisis unlike any it has faced for many years. The authorities are baffled that they are unable to solve a string of murders that happened in the city. As the number of victims continues to grow, the situation has reached a point where people are afraid to go out of their houses. Two of the latest casualties are mother and child.

The woman was reportedly driving through "gang territory" with her three-year-old son when they were shot to death. Upon investigation, the police officers determine that the weapon used is somehow connected to the unsolved homicides. The Major Crimes unit will be tapped to find the culprit and unravel the mystery once and for all. Who is the killer and what does he want? Will Sharon Raydor (Mary McDonnell) and her team be able to close this case?

To get to the bottom of things, Amy Sykes (Kearran Giovanni) will forge an alliance with a former LAPD detective with a shady past. The man has an ingenious theory on the crimes and Sharon wants to pick his mind. Will they be wrong to trust the disgraced agent?

Meanwhile, TV Guide reports that the unit will welcome a new member. Detective Stephanie Dunn, who will be played by Julie Ann Emery, will soon work with Sharon on a case involving an off-duty police officer who was murdered 12 years ago. His killer has resurfaced and the unit will be tapped to capture him. Stephanie is reportedly a widow. The case is personal for her, as her husband was the bodyguard of the prosecuting attorney who was killed alongside him. Executive producer James Duff shared some facts about the new character.

"Shattered, Stephanie drank for a month, then transferred out of homicide to narcotics investigations, but, like Sanchez, she never got over the death of her spouse ... Coaxed back into Major Crimes... Steph finds herself forced to relive the death of her husband while entertaining the possibility of joining Captain Raydor and her team as a full time member of her division," he said.

"Major Crimes" season 4 will return on Monday, Feb. 15, at 9 p.m. EST on TNT.