The Second Thirteen — James Houston Turner

Now living in Australia, Talanov and dozens of dinner guests are suddenly the target of assassins. Talanov and his wife are mistakenly spared, but soon find themselves running for their lives, hunted by the killers, blamed by the police, increasingly pivotal to an invisible network of death about which they know nothing. But someone thinks they know.

For in 1983, a second Department Thirteen was created, and Talanov discovers they have but one purpose: to kill him, whatever the cost.