Missing Spark

Talked with Jeremiah on watch last night. He was talking about some strange things, members of the crew being taken up to the top of the Spire, then coming back... different. Said it looked like the light had died in them, somehow. They'd still work, but didn't talk to anyone, didn't drink or gamble or anything. Ridiculous, right? I told him he was imagining things, and needed to get some sleep. Maybe he was coming down with something? Tried to find him earlier today to check on him, and... maybe he was right. It looked like him, but there was nothing behind his eyes. No joy, no worry... nothing. He didn't even seem to recognize me until I shook him, then he damn near bit my hand off. What the hell is going on?