Circles of Deceit: Dark Secret (1995)

One of Neil's former SAS colleagues now operates on the wrong side of the law, and Neil's bosses want him to monitor the man's activities. Neil's investigation leads him to an ambitious member of Parliament who has a history of run-ins with the security services. As usual, though, Neil has been kept in the dark about some of the details of his assignment, and soon people around him start to die.