I stepped carefully onto the 2×6 joists, balancing my weight, following the silver branch that extended toward the space above the twins’ rooms.
“Where does that secondary return drop down?” I called back over my shoulder, keeping my voice low.
Julian squeezed his shoulders through the attic hatch, his shoes scuffing the wood. “Follow the insulated trunk to the left. There should be a vertical drop right above the partition wall.”
I found it. A rectangular galvanized sheet-metal duct penetrated the ceiling framing, disappearing straight down into the wall chase below.
I leaned down near the penetration.
Nothing. Just the flat, papery smell of fiberglass insulation.
“The smell isn’t here,” I murmured.
“Emily, look,” Julian said, his voice tightening with a mixture of hope and rising panic. “The specialists at Children’s told us that if it were environmental, the markers in the blood would show elevated inflammatory cytokines or foreign protein antibodies. But their labs just show metabolic exhaustion. It looks like their cells are literally running out of oxygen at the subcellular level, even though their lung saturation is ninety-nine percent. How could an odor do that?”
