The Doctor is left all alone on the ship.
Apart from the actual explanation of what was going on in the last act (yuck, technobabble city), this was a pretty good piece of paranoid ‘what’s real here’ storytelling. It’s always an uphill battle in this type of story within an ongoing story, because the audience ‘knows’ what reality should be. But this episode manages it well.
It’s also good to see Barclay make a reappearance, and he and the Doctor work well together. None of the other crew-members really get very much time on screen at all, though.
378 down, 359 to go.