The Activity Club and the House of Frost

Isabel is looking at the door, her face scrunched up in concentration.

"Any luck?" you ask her.

"No," she says. "I've tried pushing and pulling this door. I guess the only thing to do now is... knock?"

You don't like the idea of alerting whatever is on the other side of that door to your presence, but Isabel goes ahead and knocks anyway.

Silence.

Silence.

And then...

...

Nothing happens.

"Well, no luck there!" she says. "But we've got this, Max. You visit the other doors, and I'll figure out how to open this door."

"Sounds like a plan."

Where do you go next?