Five cannibals get appointed as engineers in a high-tech company. During the welcoming ceremony, the boss says, "You're all part of our team now. You can earn good money here, and you can go to the cafeteria for something to eat. So don't trouble any of the other employees."
The cannibals promised not to trouble the other employees.
Four weeks later, the boss returns and says, "You're all working very hard, and I'm very satisfied with all of you; however, one of our janitors has disappeared. Do any of you know what happened to him?"
The cannibals disavow all knowledge of the missing janitor. After the boss has left, the leader of the cannibals says to the others, "Which of you idiots ate the janitor?"
A hand raises hesitantly, to which the leader of the cannibals says, "You fool! For four weeks we've been eating Team Leaders and Project Managers so no one would notice anything, and you have to go and eat the janitor!"