In actual practice, the use of the past perfect quite frequently
violates the mathematically precise timelines set out for it in grammar
books! It is merely an indicator that something happened in the
context of something past. Now the problem is that this past point of
view has to be established somewhere to begin with, so you can't just
begin a conversation with a sentence in the past perfect tense! On the
other hand, the past point of view does not even have to be in the same
sentence with the past perfect verb. It may have been established
earlier in the text. Also, in narrative fiction, just about everything
is in the past tense, so what is past from the viewpoint of the
story-teller may be given in the simple past, while what is past from
the viewpoint of the characters of the story may be given in the simple
past or in the past perfect, depending on how the author wants the
reader to understand the time relationships in his story. These
factors cause for a great deal of confusion.
In the sentence now under the grammar microscope, it seems to me that the
when
clause is used to establish the past point of view. A suggestion was
made in the past -- past with respect to Langdon's understanding of the
events surrounding that suggestion. Thinking back to the time of that
suggestion, Langdon ('now') saw/felt/understood that Fache had looked
smug ('then'). When? When the suggestion was made.
The author considers the reaction to the suggestion the main event -
not the suggestion itself. The making of the suggestion is no
more than a temporal signpost to which the reaction can be related.
Compare:
I recalled quite vividly how they had laughed when I told that joke.
Jerry was absolutely convinced that they had stolen the money when he left the room to answer the phone.
The Robertsons were shocked at how thoroughly their new puppy had destroyed the sofa when he was left alone for the day.
That said, all of these examples, including the one in the original post,
could have had the verb in the
when
clause in the past perfect tense! But it's unnecessary for
understanding the time relationships, and it is somewhat inelegant
stylistically -- too many "had"s, maybe?
CJ