Reaching for a Moonray. Mansion of Ghosts and Gold, #3

"Bathed in the moon's flickering light, each saw its chance, " Andy read from Uncle Proctor's old journal. "And I sensed them all grasping, reaching for a moonray."Abby's dance school is progressing, and the Banyons haven't been back to Uncle Proctor's mansion in a week. Driving home, they're ambushed by Priscilla, who demands their attention at the gloomy home for an important announcement. The extended Proctor family is offering the sale of the enormous house to them at a deep discount, owing to the departed uncle's fondness for Abby and her love of dance.
But the matriarch of the Proctors, Penelope, must first be sure that there are no ghosts in the house. With Andy and Annabeth repeating Uncle Proctor's experiments, combining Moon Metal with the echo process that had called a ghost before, can that gloomy old structure keep its ghosts hidden long enough for Penelope to approve the sale?