From the back of the book:
Enter a Realm of Enchantment
When Monsters threaten the village of Crystalbrook, it's up to adventurers to track down where they're coming from. The investigation leads them on a journey across planes. In the Feywild, the heroes must explore an enchanted island garden and unravel the plot of a foul hag, before she and her fiendish companion can perform a ritual to seize control of the island.
Beyond the Crystal Cave is a Dungeons & Dragons adventure designed for the winter 2011 season of the D&D Encounters official play program. This season incorporates character options from Player's Option: Heroes of the Feywild, and it comes with three full-color battle maps, thirteen ready-to-play encounters, and information on the D&D Encounters program.