In the Circle of Time - Margaret J. Anderson

The mist gathered slowly, just a faint coolness and dampness around the stones. . . Then Robert noted the silence. . . fog blanketed the ground within the circle of stones. Jennifer was just a gray shadow of herself, still digging down toward the hidden slab of rock. The coldness of the fog soaked into Robert and he suddenly wanted to push the soil back into the hole he had dug, but the cold seemed to have reached his brain and he had no more power over his thoughts.In this compelling time-slip novel,..