Final answer:
The children in 'A Wrinkle in Time' travel to Camazotz after the Happy Medium, where they are left alone to confront the planet's challenges.
Step-by-step explanation:
After leaving the Happy Medium, the children travel next to the planet Camazotz in Madeleine L'Engle's novel 'A Wrinkle in Time'. Once on Camazotz, the children are indeed left there alone to face the challenges presented by the planet and its inhabitants. This dark and oppressive planet is in stark contrast to the more peaceful and enlightening experience provided by the Happy Medium. The narrative focuses on themes of good versus evil, conformity versus individuality, and the power of love and courage.