On the morning of the vernal equinox in 1899, Holmes is roused from his bed by Lestrade. The inspector has received a report of a girl brutally murdered at Stonehenge.
Upon arriving at the famed site, Holmes discovers the body of a young woman. On her forehead, painted in blood, is a druidic symbol. On her side, also in blood, is a message written in a strange language that neither Holmes nor Lestrade can decipher. The girl was also eviscerated and her organs placed around her body. As a final touch, branches from yew trees had been artistically arranged around the corpse.
Holmes senses a malevolent force at work, but without data, he is powerless. As the weeks pass, he slowly gathers information about the ancient druids and Celtic mythology and begins to assemble a small army of experts to assist him.