From publisher blurb:
A 5th Edition Mini-Dungeon for 5-6 characters of level 20
We find the characters resting in the private rooms of a grand inn after their latest adventure. One wall holds a huge floor-to-ceiling painting of a vast landscape. On the left is a lofty mountain, its pinnacle wreathed in fog; the right has a squat volcano with a trail of ash and embers. Twin suns sit above it all.
A roaring fire and rich food pushes the heroes toward sleep, but as they doze, their hostess, the disguised Red Queen enters to clear items away and lower the fire but instead flings down three beads from a necklace of fireballs and steps through the mirror.
Although the mirror’s reflection shows the characters fast asleep, they find they can follow the Red Queen through the glass into a similar room—but in another land.
Looking back, they see their sleeping reflections in the original room.