I was thinking of there being an on going joke with Tadhg about how, while in California for 3 months, he did nothing California-y.
He didn't go to the beach because he assumed they were closed in the winter. He walked his dog at a park inland because he thought the high surf might scare him. He didn't go to Disneyland or that part of Hollywood with the stars. He stayed in the hotel and watched tv a lot... might have rekindled his interests in horror and mythology which becomes useful.

from a lucid dreaming site concerning "shared dreaming:"
"Use your feeling of the person. Everyone in dreaming has a unique energy signature you can recognise them by. It is a subtle feeling of simply knowing THAT person IS that PERSON, no matter how they may appear to you.

Once you have this feeling of the person. Focus that feeling to change dreams and the dream you wind up in will be that persons."

I imagine, when Tadhg was in the hospital, Tabbi was so worried about him she ended up in his dreams because she could feel his pain. Now it's very easy to find each other...

When Sophie curses them, they're forced together, which leads to headaches and illness the next day.