The people of Pembrose have long believed that King Arthur and the sorcerer Merlin once lived near their small town. In fact, the cave where Merlin did his magic is a popular attraction for visitors. But now a handsome archeologist has come to town claiming that the cave is just a hoax, a legend to attract tourists. Minerva, Ravi, and Thomasina believe in the legend and in Merlin. Once they prove it to the scientist, the three friends can get back to the mystery of Minerva's missing parents.