Paul has been through a lot in the book of Acts! Beatings, shipwrecks, whippings, imprisonment; just to name some of it, and despite it all the Gospel cannot be stopped.  The book of Acts ends quite abruptly with no official ending, which seems to make a profound statement that the book is not  about Paul or Peter or Barnabas, but about the continuing of the story of God redeeming his people into a life-giving relationship.