Dashiell Hammett said this quote
“ When a man's partner is killed he's supposed to do something about it. It doesn't make any difference what you thought of him. He was your partner and you're supposed to do something about it. Then it happens we were in the detective business. Well, when one of your organization gets killed it's bad business to let the killer get away with it. It's bad all around-bad for that one organization, bad for every detective everywhere. Sam Spade ”