The highlighted part of the sentence is called a/an Professor Plum , who had been to the mansion before , expertly navigated the maze of rooms andcorridors to quickly reach the conservatory
I think this is what you are wanting to know. You would use a not an If the word/name (Professor Plum) would have been something starting with a vowel instead, you would use an
Is this what you were asking?
I would like to give you a simple background about figurative language and sensory imagery.
The sensory details or figurative language used to describe, arouse emotion, or represent abstractions. On a physical level, imagery uses terms related to the five senses: visual, auditory, tactile, gustatory, and olfactory. On a broader and deeper level, however, one image can represent more than one thing. For example, a rose may present visual imagery while also representing the color in a womans cheeks and/or symbolizing some degree of perfection. An author may use complex imagery while simultaneously employing other figures of speech, especially metaphor and simile. In addition, this term can apply to the total of all the images in a work.
He Goes to Bars Because he was upset