Perhaps, she said; and then swiftly passed out of the little glade, leaving John standing there as though he had been turned to stone. 
John was literally turned to stone. He saw a Medusa. 
mnli hypothesis: John was literally turned to stone. He saw a Medusa.  premise: Perhaps, she said; and then swiftly passed out of the little glade, leaving John standing there as though he had been turned to stone. 