After the revelation regarding Riley and her true colors, this episode is a nice bit of subtle plot progression. Sarah is still nutty over those three dots, and while the characters themselves seem to be wondering about her objectivity, the viewers have yet another reason to think she's more sane than she feels. Meanwhile, Cameron's nighttime activities are revealed, and they are more interesting than suspected.
It's one of those stray questions that might usually be left to imagination: what does Cameron do when everyone else is asleep? The easy answer would have been "guarding the Connors". But that's exactly the point; that would have been the easy answer. Instead, the writers show us what she's really doing: using her infiltration skills to open up doors for research and intelligence gathering. It's not at all the obvious answer, but upon reflection, it makes a great deal of sense.
It's even more interesting to consider that Cameron's research might have found an explanation for those three dots. While she resolves a potential threat and stops a plot by SkyNet (to what purpose, we don't yet know), she reveals how the terminators identify the time period in which they arrive following time travel. They essentially use three marker stars in a triangular pattern as a basis for calculating position relative to time.
One can only assume that this is intentional on the part of the writers, though it's hard to imagine how it could be applicable to the blood marks on a wall. The positions of the stars would be relatively stable from a human's point of view, and any changes within a short period of time would be subtle at best. So it's more likely that this is a play on the notion that Sarah is mistaking pattern recognition for significance. The viewer is left to wonder: was that why the pattern was meaningful, or am I falling into the same psychological trap?
Along the way, Cameron displays her usual unusual version of human interaction. On the whole, Cameron was actually trying to be nice to her new "friend", and wanted to see to his well-being. Unfortunately, she has the social skills of a toaster, so she does the right thing in the wrong way. And, of course, she misinterprets appropriate social cues. For an infiltration model, she must be more damaged than anyone imagined. Because unless people assume she's suffering from mild autism or something, she doesn't exactly blend. (And that's not even taking her unusual beauty into account.)
The subplot in this episode has Riley twisting John around her little finger, as per Jesse's orders, and she does a pretty nice job of it. Now that we know she's playing John, her sob stories take on a sinister edge. The writers will need to continue on this subtle path, and avoid the temptation to have John make too obvious a mistake. It should never look like John is overlooking some obvious detail, since he's already making some boneheaded moves as it is. Kudos to the writers for making Riley's deception believable!
At the mid-point of the season, the characters continue to undermine their mission with their personal hangups and lack of confidence. There's the sense that something truly horrific will need to happen to force them to get their act together, and with the holiday hiatus coming soon, it may not be far off.