Rojas reunites with her former foster care caseworker, Ben. He needs a favor as a homeless man he was working with went missing right before his big job interview.
Rojas agrees to look into it because Ben was "one of the good guys."
Unfortunately, Roberto turns up dead a few hours later much to Ben's dismay.
Voight agrees that they will take over the homicide and they begin to look for clues as to what happened.
They visit a church that has become a haven of sorts for the homeless and talk to Sammy, Roberto's good friend.
Sammy informs them that they were being followed by a blue pick-up, which he believes is the CIA.
Intelligence looks into the claim and tracks down Joe, who was with Roberto hours before he died.
Joe admits that he did point a gun at Roberto who stole his cocaine but that he simply retrieved it and left.
Intelligence checks out the house where Roberto was squatting in and find one of Sammy's books, which means he lied and knew where his friend was living.
They go to confront Sammy at the church, but he's gone. He took all of his belongings san a pair of bloodied shoes that puts him at the scene.
After talking to a few of Sammy's old law professors, they learn that he was diagnosed with paranoid schizophrenia and that he's a compulsive reader.
They find him at a used book shop but when he sees the police, he makes a run for it.
After a tense-stand off with Rojas and an overeager cop, Sammy puts down his knife and surrenders.
During the interrogation, he admits that he was in the house during the murder and saw what went down.
He describes the man as someone who claimed to be a social worker, Hispanic, and with a goatee.
Upton suggests that maybe Sammy is making it up but Halstead confirms someone is trying to use Roberto's identity.
They're able to track down the man, Eduardo Salazar, and eventually find him at a store attempting to take a passport photo.
Eduardo was being hunted for two murders including the murder of a cop.
Rojas learned that Sammy escaped from the hospital where he was being held. She and Upton try to track him down at the church and learn he came by and stole a gun from one of the men.
They track him down to a closed down bookstore where Sammy seems to believe that Rojas gave him a phone to listen to his thoughts.
When he hears cop sirens, he begins shooting his gun into the air and makes a run for it.
They chase him down into a local convenience store where he attempts to shoot a man who resembles Eduardo because he believes he's coming for him.
As he rushes towards the man and his daughter, Rojas shoots him in the chest.
Once he's down, she realizes he never had a gun.
Voight sees how distraught Rojas is about the case and tells her the CPD found the gun.
She visits Sammy in the hospital. He's stable but unconscious. She gives him a book and breaks down by his bedside.