The glass is designed to be looked through, not at. The glass is supposed to disappear.

The smear caught the light at 16:50, exactly when the sun had dropped low enough to make it visible.

She moved directly to the panel — not searching for the smear. She knew exactly where it was.

She did not look at the sea. She did not look at the sky the glass was reflecting. She looked at the specific square centimeter that required her attention. The concentrated focus of someone who has learned to see maintenance instead of beauty.

At this hour the glass is converting the golden Aegean sunset into electrical current into hydrogen pressure into the number on the gauge three decks below.

It is working perfectly.

She finishes. The smear is gone. The glass is invisible again.

She moves to the next panel.