There were two kinds of punch - with and without booze - and when a straightlaced coworker asked which one was which, some bratty pranksters from the support department told him the wrong one.
Half an hour later, I was sitting with the guy under a tree. He was smashed completely, and wagged an accusing finger.
"I don't get drunk. That's the kind of thing you would do."
I took offense, and he wagged his finger again, "No, not you, Ted. You, you humans."
...and then he told me his story. That there were two species of sapient hominids living on the planet, one in hiding. Ur-Humans, they sometimes called themselves. His species, he told me with a drunken slur, were similar in appearance to humans, but lacked the human self-destructive instinct. A doctor or a psychologist would be able to tell the difference with a little investigation, but the Ur-Humans never need a psychologist, and on the rare occasions when they need a doctor, they see an Ur-Human doctor.
He told me that each person is his own worst enemy. He told me alcohol had power for humans because it made it harder for them to punish themselves.
The Ur-Humans live among us. They vote in elections - conservatively. They shop at the same stores, but don't buy junk food. They exercise regularly, have peaceful family lives, and have mild but insightful tastes in art and literature. They don't have televisions or automobiles. They're not running the world, because they lack the self-loathing required to want to dominate those around them.
No Ur-Human had ever betrayed the secret before. He would not have done so, ever, if he hadn't been maliciously poisoned.
Today, he didn't show up to work, and his desk was cleaned out.