the tell: preferring the solitary high to company
The way he knew suddenly that he was going to go down and get high in secret in the Pump Room before showering was that it hadn’t occurred to him to ask The Darkness about making some sort of arrangements to eat together, since Stice had missed supper too.
Context
The textbook diagnostic caught from the inside: Hal reads his own coming relapse off a negative space — the fact that it never even crossed his mind to eat with a friend he likes, because the private high has quietly outcompeted company. He knows he's going to the Pump Room not by wanting it but by noticing he'd rather be alone, which is the exact tell that the solitary using has become the preferred appointment.