From the back cover of the first printing:
THE VIXEN'S WARNING
The beautiful red fox lures little Claudia to the forbidden house on the hill. Claudia summons the twins - Charles, the dreamer, and Janie, the genius - and sensible Alys, who never imagines what evil lays waiting for them.
THE AMULET
Together they find the spell to make an amulet that lets them pass through the moonlight mirrors into a world of bright magic and dark enchantments.
THE MISTRESS OF MIRRORS
The great sorceress, Morgana, is imprisoned somewhere behind the silvered glass. Only Claudia and her friends can find and free her. Only she can lead them in battle against the terrible evil waiting to burst into the human world on...
THE NIGHT OF THE SOLSTICE