My party consists of five people across multiple states playing using roll20. Because of people traveling for the holidays, all but one of us will be near the same place, so we're going to have our first in-person session, a one-off where they'll have to climb a tower, fighting enemies and solving puzzles.

I've set it up where the absent player is trapped at the top of the tower near the big bad and they're going to charge up and rescue him.

My idea is that he can overhear what the boss is saying and communicate telepathically with the rest of the party to tell them hints about puzzles or enemy weaknesses and such. He's down to do this by phone or text.

Does anyone have any ideas for puzzles that could incorporate the missing member in a fun way?