Complex sentence: Here he is visited, unexpectedly, by Dinmont, who has heard from Gabriel of his being in danger, and manages to convince McGuffog to allow him to stay the night in Harry's cell.
Split into simpler sentences: Here he is visited, unexpectedly, by Dinmont, who has heard from Gabriel of his being in danger. Dinmont manages to convince McGuffog to allow him to stay the night in Harry's cell.