In a sentence like this from Simon Starling’s story:

“Where had he seen those little arms and legs before?”

..there are actually traces everywhere from the movements of the particles (this is one theory anyway, which is deliciously called “Government and Binding Theory”, and of which I’m trying to remember small parts).

At an earlier point, on an underlying mental level, the sentence would have been more like this:

“He had seen those little arms and legs before [in some place].”

and then the “in some place” turned into “where” and moved into question position because it’s unknown, and leaves a trace like this:

“[Where[i]] he had seen those little arms and legs before [trace i].”

and then the infinitive [had] moved up too because it’s a question, and it left another trace:

“[Where[i]] [had [ii]] he [trace ii] seen those little arms and legs before”

You could be much more detailed and follow all the crazy traces that make the sentence past tense, and insert the adjective, and inflect the verbs and conjugate the nouns with case, even though case doesn’t show on the surface in English.. but my point is that sentences are stacked full of traces even before we think about what the words refer to outside the grammar.

And then, above the level of the grammar, “he” means someone we’ve met elsewhere in the text and who we’ll meet again, and so there’s a bigger, discourse-level trace which leads out of the sentence and out into the rest of the text.

And then “those little arms and legs” have a trace earlier on in the text (the “those” indicates this), but also have a trace that we can’t access: in the history of the fictional character within the text – and so in some sense can be traced back to some (even more?) fictional part of the fictional narrative. And oddly, that super-fictional place also traces back here to this very sentence we’re looking at, in the word “before”, while it also traces forward to the character’s realisation of where/when he’d seen them before, which we witness later.