Reporter Julie Cannell calls Cal and wants him to determine if the source she's meeting at a hotel is telling the truth. When she enters her room, the source is already there; he hands her an envelope and asks to leave. She begs him to wait.
Cal comes home and finds Emily upstairs with a boy, Rick. Cal is unhappy. He'll take Rick home, but first he'll meet Julie. Emily rides along, saying, "It's just sex, Dad."
Cal enters the unlocked hotel room, finds Julie dead, and sends the teenagers away. Ben and FBI honcho Dillon arrive, explaining that the subject of Julie's story -- Darryl Anslinger, an ex-cop who is now a city councilman -- is also the focus of an FBI investigation.
Cal persuades Dillon to let him observe Anslinger's reaction to news of the murder. Anslinger is surprised, adding that the story Julie was writing was pure fiction. When Cal asks Dillon if he is pals with Anslinger, he gets stonewalled. When they leave city hall, Cal spots a man hurrying away.
As Gillian tells Ria to go to the newspaper and get Julie's notes on Anslinger, the suspicious man arrives at the office, saying Julie was killed because she met him at the hotel, followed by two Baltimore detectives. Cal says stall the detectives, and he leads the man down a staircase.
The man says he is Bo Hackman, and Anslinger hired him to kill real estate mogul Steven Cook, but he couldn't go through with it, so now he's a target. The now-missing envelope he gave Julie contained evidence of this. He'll give Cal a copy. When Cal asks if Bo went to city hall to get to Anslinger first, he's noncommittal, then runs.
One detective gives chase. The other tells Cal that they came to the office as a routine follow-up. Cal asks if they're working for Anslinger or the FBI and gets no real answer. Ria, who's been listening, tells Cal that their story is bogus. Cal wants Ria to find Cook, sending Eli to the newspaper instead. Cal also wants Gillian to have a sex talk with Emily -- who's been sitting in Cal's office -- after dinner at their house tonight.
Cal and Gillian question Anslinger, who says that for years he's been blocking Cook's plans to redevelop property that's currently a housing project -- and he didn't need him dead to stop him. They head for Cal's home and find the two detectives inside, claiming the door was unlocked. When Emily, who'd gone to the store, returns, she denies this. Cal orders them out, and he and Gillian agree that the detectives wanted to convince them that they were working for Anslinger. She says she'll talk to Emily another night.
When Ben and Ria go to question Cook, a man tells them that Cook -- fearing for his life -- is unavailable. Meanwhile, Dillon orders Cal to investigate another case. Ben asks Cal if his past history with Dillon was based on science. "Sometimes it's just a feeling," replies Cal, who gets a call, then tells Ben to handle the other case himself.
Cal goes to a train station, sees Hackman with the envelope, and watches him get killed as the envelope is stolen. Ben appears, chases the gunman, and takes three bullets to the chest. Cal rips open Ben's shirt and discovers he's wearing a wire. Dillon arrives, explaining Ben asked for the wire to prove that Cal's beef with Dillon was based on science. Hearing the tape, Dillon threatens to suspend Cal's FBI contract.
Then Cook arrives at the Lightman office and Cal -- noting everything is too convenient -- asks Dillon to observe the interrogation. Cook accuses Anslinger of corruption, denies knowledge of the envelope -- he's lying -- and asks if they've searched Anslinger's office, house, and condo. Cal notes this scares Dillon.
Eli, who's been going through boxes of Julie's files, says she knew about the condo: Anslinger met hookers there. Cal asks Dillon why he didn't mention this. Cal also thinks Cook's problem with Anslinger is personal.
Cal and Gillian call Anslinger in for questioning. Eli reports that the FBI found a paper shredder in the condo and that Cook owns the newspaper where Julie worked. Cal puts Cook in the cube with Anslinger. When Cook mentions the shredder, Anslinger looks relieved. Cal says Anslinger didn't want evidence of his kinky sex habits exposed.
Cal explains that Cook hired Hackman to fake the attempt on his life -- and the detectives. The envelope was bait so Julie could be killed by Hackman to frame Anslinger. Then Cook had Hackman (and nearly Ben) killed.
Cal produces a DUI that Cook received from Anslinger 20 years earlier. Anslinger also arrested his passenger on fictional prostitution charges, dated her, then dumped her. Cook, who Cal says has wanted payback ever since, attacks Anslinger, who wraps him up. Dillon arrests Cook.
On his way out, Anslinger notices Julie's files all over the office floor. Cal says, "We're going to get to know each other well."
When Cal gets home, he warns Emily that Rick will say anything to have sex with her. Emily replies that they never did, she just said that because she was angry -- and she lost her virginity two boyfriends ago. Cal, troubled by this, asks why he should trust her? Emily says because she's smart, he's a great dad -- and he has no other choice. They hug.