Spaceships are fused and everyone on board is having a bad trip - some in more ways than one. But will there be enough positives aboard the Empress to make this a first class excursion for special guest Derek O'Brien, who brings the perspective of a visiting American discovering Doctor Who for the  first time? And do he and your host Toby Hadoke stand any chance of finding common ground in their likes for this story, or is a there a big gap of nothing between them...?