If I remember correctly, the timing of Stokes's arrival was such that it could be assumed, though it was not in any way said, that Stokes figured out how to rescue Barnabas from his latest Perils-of-Pauline situation. In fact, it just occurred to me that Stokes might have come to 1840 specifically in order to effect that rescue. I'm imagining that in 1970, during construction of a new building, something interesting was found that worried Stokes, as a result of which he dashed off to the Quentin's staircase. Unfortunately, the dialogue doesn't support this theory. Details, details.