|Series 04, Episode 05|
|Air Date||6 October 2005|
The Book is the fifth episode of spook's fourth series which aired for the first time on 6 October 2005.
Journalist Gary Hicks witnesses the murder of Clive McTaggart, a high-ranking retired intelligence officer and friend of Harry's who was about to publish his memoirs, which contain government secrets. While MI5 investigate and Hicks attempts to publish the story, a group of people from the government is sent to kill him.
Meanwhile, spook to-be, journalist Jo Portman follows the investigation, and Adam, impressed by her skills that lead to a major break in the case, recruits her by the end of the episode. In the end, Taggart mailed Harry the memoirs in the event of his death.