Big Bad: Grady Memorial Hospital and Dawn are cemented as this by this episode.
Brass Balls: Noah, according to Daryl when he's being threatened by him.
Daryl: You got some sack on you, for sure.
Character Development: The episode spends most of it's time focusing on Daryl and Carol questioning if they've really changed since the apocalypse began.
Continuity Porn: Lots of references to previous episodes in the series are made.
Flashbacks throughout the episode focus on Carol disposing of infected corpses, when she was exiled from the prison by Rick, when she discovered the ruins in the wake of the Governor's attack, and right before she reunited with Rick and Daryl after Terminus.
Daryl and Carol entering Atlanta is a shot for shot reference to the iconic shot of Rick entering the city in the pilot.
It may not be the exact same tank, but the shot of a derelict tank is another reference to the pilot.
There are scorch marks in the streets from the napalming of Atlanta, an event referred to several times and seen in a season 2 flashback.
The walker that only has half it's torso is a clear nod to the first walker Rick encountered during the pilot and later put down.
The child that turned clearly served as a cruel reminder of what happened to Sophia, as few child walkers have been seen since.
Daryl takes a book instructing how to treat victims of child abuse. It was revealed in "Home" that Daryl and Merle were victims of abuse at the hands of their father, with Daryl taking the brunt of it after Merle abandoned him.
Similarly, Carol mentions her past as Ed's battered wife.
Everyone Loves Blondes: When Daryl asks Noah for Beth, he mentions her blond hair. In turn, Noah immediately figures out its Beth upon hearing it.
Foregone Conclusion: We know from "Slabtown" that Carol will end up a captive of Grady Memorial, and from "Four Walls and a Roof" that Daryl returns to the church with a companion, but this episode shows us how it happened.
Gut Punch: What seeing the child walker very clearly is for Carol.
Hold Me: Before their van goes off of the bridge, Carol grabs Daryl's hand for comfort.
Throwing the Distraction: Stuck in an overrun city and with limited resources, Daryl and Carol rely on stealth and distracting walkers more than in most episodes. Daryl improvises a distraction by throwing a pack of paper he lit on fire into the street.