This is an emotional episode. It shows a very harsh reality to the zombie apocalypse. There is already a glimpse at various versions of madness. We have see Rick's trip to "Crazy Town" and the megalomania that has consumed The Governor (and Andrea for that matter, but we can discuss that later).
I imagine that a lot of people wondered what could possibly make Rick and Co. just drive on and leave Backpack Guy in the dust...TWICE. For one, do they know anything about this guy? He could have been a lunatic...and then there is the matter that Rick had his son in the car with him. To put it simple..."Strangers = Bad."
Once they Rick's old home...there is a reunion of sorts with Morgan (the man who saved Rick in season one). Sadly, Morgan has tripped offline after first witnessing the death and then undeath of his wife. And then his son (who is about Karl's age). I believe this scene will be the catalyst for Rick to snap out of his problem and return to the role as a leader. The opportunity to look "crazy" in the eye might have been the wake up call that Rick needed.
Other moments of note: we get to see more depth to Michonne (ugliest papier-mache cat ever) and more of the maturation of Karl. The episode ends with a "call back" to the opening scene. It is no real surprise that Backpack Guy ended up dead. No sense leaving a perfectly good backpack full of supplies to rot beside the road, right?