When McNulty dumps an unsolvable murder on Rawls' division, Ray Cole is the one who has to work the case. McNulty feels bad for Cole, but claims that he is just collateral damage – his real intent was to mess with Rawls' stats. Bunk and Lester begin to feel that they are also victims of McNulty’s “collateral damage”.

This could also refer to the issues that the stevedores now have to deal with as the result of Valchek’s attack against Frank Sobotka, such as the DUI checkpoints.

This most obviously refers to the sentences given out to members of the Barksdale organization. Avon gets 7 years, Wee-Bey gets life, D'Angelo gets 20, and Ronnie Mo gets 15.

It also refers to McNulty’s unofficial “jail sentence” when he is kicked out of homicide and stuck on the marine unit.

This refers to the doubt, fear, and animosity characters in the show are beginning to experience:

• Marlo has his doubts that Little Kevin said nothing to the police, which is why he has him killed
• Bodie has his own misgivings as to whether or not he should be working for a man like Marlo
• Colvin, Parenti, and a few other teachers take issue with administration insisting that even the “corner kid” class is taught for the test
• Carcetti has his fair share of misgivings when it comes to trusting Senator Clay Davis
• Students at the school begin doubting Randy’s integrity and start treating him like a snitch
• Burrell begins to fear for his job as Commissioner
• Daniels takes his misgivings about Burrell’s attempts to “juke the stats” straight to Carcetti
• Bubbles starts to feel like he can no longer trust Herc, which is why he gives him a bad tip that gets him in trouble

This refers to changes made by both the police and members of the Barksdale organization in the wake of Kima’s shooting and the subsequent hunt for the shooter.

BARKDALE ORGANIZATION

• Stringer collects the pager of everyone who works at the pit and instead gives cell phones to Bodie and D
• Dealers are given instruction to only conduct business face-to-face
• Stringer and Avon distance themselves from Orlando’s, as Levy feels there is a chance Orlando was talking to the BPD
• Stringer becomes the de facto head of the organization to draw attention away from Avon
• They begin planning to kill witnesses that could incriminate the entire organization, which leads to the eventual murder of Wallace and the security guard that almost testified against D'Angelo before she was paid off

BALTIMORE POLICE DEPARTMENT

• McNulty gets his act together, stops drinking on the job, and re-dedicates himself to the detail
• Prez begins chasing a paper trail of non-drug money in hopes of making a higher level arrest
• Lester tries to get information from a Barksdale business meeting by hooking up a dancer from Orlando’s with a wire
• The unit successfully installs a camera in the wall of Avon’s office by the end of the episode

This refers to the BPD’s hunt for Kima’s shooter, as well as Major Crimes' internal hunt for the snitch that is leaking info to the higher ups and hurting their case against Barksdale. (Little Man turns out to be the shooter and Carver is the rat)

Pretty straightforward (though these things get progressively more complex) – the Baltimore Police Department’s new target becomes Avon Barksdale after McNulty circumvents the chain of command to talk to Judge Phelan.

This is taken from the proverb “Do unto others as you would have them do unto you” – basically treat others the way you wish to be treated.

This is relevant because Omar has to deal with fellow inmates that he robbed and now want revenge on him. He didn’t treat them very well, and now he’s in danger because of it. It also refers to how Crutchfield threatens to mess with Bunk’s next case after Bunk attempts to unsolve Crutchfield’s last murder and vindicate Omar in the next episode.

This refers to all of the characters in the show left “without a home”. Kima, Lester, and most of the Major Crimes Unit had to search for new jobs after Lt. Marimow all but shut it down, and Bodie has to work his own corner in the wake of the collapse of the Barksdale organization.

This is an obvious reference to the home rooms the students are assigned to on the first day of a school, but more subtly refers to the living situations of Omar and McNulty. We see a pretty intimate scene of Omar and his boyfriend Renaldo waking up together, and learn that McNulty has stabilized his life after settling down with Beadie and quitting drinking.

Carcetti reveals to Reverend Franklin in the beginning of episode that he is within the “margin of error” for these mayoral surveys. Meaning that he is losing to Royce now, but it wouldn’t take a lot for him to win the next survey/poll.

It also refers to the slim margin of error each candidate has to operate with if they want to win the election. Carcetti flips out at the sight of a photoshopped flier showing him shaking hands with a hated Baltimore slum lord in this episode. Norman assures him he can use his contacts with The Baltimore Sun to prove the photo is fake, but Carcetti is still upset because he knows the election could come down to the success or failure of a juvenile smear campaign like this one.