Written as a stand-alone but clearly connected to the larger season premise, this is a solid, gritty episode that fleshes out the relationship between Derek and Jesse while telling a more complex story in the process. The writers for this show never seem to go after a plot point in the obvious way, and that trend certainly continues.
John Connor, hero of the future, never shows up in this episode. Even Cameron is barely present. I would even say that Sarah is barely in the episode, though her leadership presence informs everything. This entire situation appears to be based on one of the names written in blood in the season premiere, and as such, represents something of a vindication for Sarah. I can't imagine that Derek has much doubt left now.
After all, the dots connect in a way that Derek cannot deny. Sarah sees the name on the wall and finds the family at the cabin. Sarah's decision to save them toughens up Lauren and leads to the birth of Sydney, which Derek is there to see with his own eyes. Lauren and Sydney, in turn, grow up to be the ones who save Derek and Jesse from a plague unleashed on the Resistance. Ergo: if Sarah didn't follow the lead provided on the Wall of Blood, the future would have changed.
Granted, the rules in the Terminator mythos are fairly loose and mutable, but Derek seemed to see how the pieces were fitting together and looked genuinely in awe over the whole thing. Not so much as to affect his competency in any telling way, but enough that he might finally stop questioning Sarah on her conclusions. (Perhaps Cameron mentioned the possible three-dot interpretation after the previous episode as well.)
Even the annoying Fields family politics did little to detract from the episode; it provided a couple of twists and turns and set the stage for Lauren's toughness. If she was used to being more mature than her own parents, then I suppose she was prepped to take care of her much younger half-sister. Perhaps a bit of a simplification, but considering the fact that we knew Lauren survived from the very beginning of the episode, the writers had established her resolve.