A Shoelace, a Paperclip, and a Pencil: The Reckoning

Tom Cooper had two strange events during his younger days which it seems might be interconnected. One of them, in Bonn in the mid-seventies, involved his temporary custody of a briefcase containing a shoelace, a paper clip and a pencil. The other was in Belfast in the mid-eighties. Tom begins to believe there might be something hidden in the briefcase: a coded message, maybe for the IRA, especially with Tom being the virtual double of an IRA operative.
Tom and his wife Liz start trying to piece together the links, at first focusing on the contents of the briefcase.
What unfolds is a chain of events which threaten Tom's and Liz's lives. Tom twice nearly loses his life and on one occasion his wife Liz does too. All, it seems, because someone, or some people, do not want them to discover the code and try everything to ensure they don't. From being hunters, Tom and Liz are now the hunted.
Those implicated in the secrets held by the briefcase continue to want Tom and his wife silenced. Meanwhile, Tom has decided "enough is enough" and hatches a plan to reckon with those wanting Liz and him dead. The problem for those around him - including not only Liz, but also the police who have a keen interest in the case - is only Tom knows what the plan is.