Wrestling with the monsters of the story for days before I run across a quotation I have seen before:
Therefore I see no wrong in riding with the Nightmare to-night; she whinnies to me from the rocking tree-tops and the roaring wind; I will catch her and ride her through the awful air. Woods and weeds are alike tugging at the roots in the rising tempest, as if all wished to fly with us over the moon, like that wild, amorous cow whose child was the Moon-Calf. We will rise to that mad infinite where there is neither up nor down, the high topsy-turveydom of the heavens. I will ride on the Nightmare; but she shall not ride on me. — G.K. Chesterton
And ooh boy is there going to be a Nightmare in the story. Not even a convenient monster for an episode, to complicate their lives. A Nightmare crucial to the plot.
Now I just gotta work out the details on how. Plus of course work out exactly how to describe the gaunt -- nightmarish appearance. (The basic idea of which I lift from a G. K. Chesterton story, rather than the essay with that. But file numbers gotta come off.)