The confession of a prisoner leads Mycroft Holmes to the trail of an island that is not marked on any sea chart. Far out in the northern Atlantic, clues are said to be found regarding what drives the murderous Circle of Seven to its bloody crimes. An expedition is equipped to search for the mysterious isle. It quickly becomes clear that the inmate has spoken the truth, as suddenly an unknown adversary has a strong interest in ensuring that Oscar Wilde and his companions never reach their destination, resorting to murder and sabotage in the process. However, Oscar Wilde is determined to uncover the dark secret of the cold piece of rock.