Beyond the Crystal Cave (UK1), adventure for AD&D 1st ed, by Dave J. Browne, Tom Kirby and Graeme Morris.
“Fleeing the rage that consumed their feuding families, Juliana and Orlando fled to the Cave of Echoes, where it is said every wish is granted. Two years have passed, and all attempts to return the lovers to their parents have failed, though some believe them lost in the enchanted garden beyond the cave. Many are the rescuers venturing into that enchanted park; a few have returned after long absences, their minds and memories curiously disturbed. Now, the handsome reward offered for the return of the lovers has tempted you, but who knows what lies beyond the Crystal Cave?”