the one thing you're encouraged to rat on

The House's single bright line drawn clean: everything else Staff must ferret out of the gossip themselves, but a resident is actively encouraged to inform on another for picking up a Substance — because relapse is the one infraction that is the disease itself, the thing the whole institution exists against. The population is named in the same breath (twenty-plus bored, crammed, street-canny people in detox from wrecked lives), which is why the line has to be that stark: the machine survives only by making the drug, and the drug alone, the unforgivable secret.