german zeppelins rain down death on London, and dr watson is grieving for his nephew, killed on the fields of france. A cryptic summons from Mycroft Holmes reunites Watson with his one-time companion, as Sherlock returns to the capital after years in retirement, tasked with solving three unexplained deaths. A politician has drowned in the Thames after giving a pro-German speech; a soldier suggests surrender before feeding himself to a tiger; and a suffragette renounces women's liberation and throws herself under a train. Are these apparent suicides something more sinister, something to do with the mysterious Spirit Box? Their investigation leads them to Ravensthorpe House, and the curious Seaton Underwood, a man whose spectrographs are said to capture men's souls...