This is book number 2 in the Mycroft Holmes series.
A gruesome display of corpses on the frozen Thames spells doom for Mycroft Holmes. Scotland Yard singles him out as the main suspect of a series of violent crimes, because they're all connected by a single thread: Mycroft's name. As public attention rises, he fights to avert any danger to his family and the Secret Service. To capture the culprit, Mycroft has to face an exceedingly uncomfortable truth about himself, which puts not only his career, but his very life into question.