Hunted: Patterson, Holmes

When former SAS captain David Shelley goes looking for an old comrade who has taken to a life on the streets, he finds his friend is dead. An MI5 agent contacts Shelley and arranges a meeting. All the signs point to murder, and the agent believes this is part of something much bigger.
The only way Shelley can discover the truth is to put himself on the streets, and into the same danger that got his friend killed.