I loved the main story, in which Cameron starts by looking into ancient siege weaponry, but accidentally discovers a photo of a terminator she knows, who was around in 1020. Of all the episodes so far, this one has the most incidental humor. Also, being set mostly in the past, it has the least contemporary mayhem and tragedy. The mystery story line is a fun and fanciful reimagining of the real estate boom of the 20's in Southern Californa, with a terminator in the mix.
Within the Cameron story line there are two subplots; one about her search for that other terminator and his mission, but another one about her "friendship" with librarian Eric, who is a cancer survivor in a wheelchair, and is clearly flattered by the attentions of this beautiful, strong and intelligent young woman. Cameron isn't, of course, very good at being a friend in one sense, and ultimately Eric tells her so. Yet in another sense, she is the best friend Eric could hope for, warning him that his cancer has returned, and that he should seek treatment immediately. This is great storytelling, playing to the strengths of the sci-fi genre.
On the other hand, we have the Riley-John subplot, which is fairly pedestrian. Since we already know Riley is manipulating John on Jesse's orders, it adds little to the story other than to suggest she's getting through to him. Overall, yet another great effort on the part of the creators of the series.