The Letter Slot
You crouch and peer at the brass letter slot. Engraved above it, worn shallow by thumbs:
I follow Woden's day. I flee Frigg's. A grey cat wears my name. Say me where the address is written, alone, after the slash, and come in.
In other words: go to the top of your browser, and change the end of this page's address to the missing day. Just the day. One word. The door is listening.