Both Uses of

glimpse
in
Murder On The Orient Express

Inside, Poirot caught a glimpse of Mr. Ratchett sitting up in bed.†
Chpt 1.4 *

glimpse = a quick look or partial understanding

I just seem to remember a glimpse of some scarlet silk affair passing the door.†
Chpt 2.2

Definition:

a quick look or partial understanding

The exact meaning of glimpse can depend upon its context. For example:

"I caught a glimpse of her when I was walking to class." -- a very quick look
"I glimpsed at the headlines." -- looked quickly
"Reading the book gave me a glimpse of the life of a devout Muslim immigrant in America." -- a quick, incomplete view