Make sure the neighbors understand that even the slightest detail that seemed out of place can be important.
-- Sean Ryan (Chapter 2 paragraph 23)

Importance: This quote reveals the new methods by which Ryan now investigates any crime scene which are based on the techniques as taught by Eugene Francois Vidocq and are now standard policy.

What would I need to do to become a detective?
-- Constable Becker (Chapter 2 paragraph 85)

Importance: This question reveals Becker's interest in going from being a Constable to becoming a detective. It is this drive and ambition that keep him at Ryan's side as he investigates this high profile murder.

We need to clean him thoroughly before he comes into the office.
-- Dr. Snow (Chapter 4 paragraph 7)

Importance: After reading the note from Ryan, Dr. Snow recognizes the potential for disaster. Afraid to restart the cholera epidemic he'd only recently helped put an end to three months earlier, he takes extra precautions.

All other murders look pale by the deep crimson of his...
-- Thomas De Quincey (Chapter 5 paragraph 23)