"She may have decided to stop here regardless," Childermass points out, "Even if she knew. Don't assume a fairy is going to think the same way you or I might."

What seems dangerous to mortals isn't going to seem as dangerous to fairies, as they simply aren't mortal. A kidnapping here or there, what's the harm? Even though just kidnapping wasn't the full extent of the danger. He's not sure he has to go into detail for Strange, however. The man's been to war, after all.

"And if the carnival ever does stop unplanned, I do not think we'll like the outcome. What else could be powerful enough to do that?"

Another fairy? Something worse?