Vice and disappointment and vindictiveness are the best of all detectives.[Les vices, les désappointements, les vengeances sont les meilleurs agents de police.]
There is no detective in England equal to a spinster lady of uncertain age with plenty of time on her hands.
Do you not know that all celebrated detectives have brothers who would be even more celebrated than they are were it not for constitutional indolence?
All detective work is, wiping out your false starts and beginning again.
A detective don’t like to be told things – he likes to find them out.