The Last Witnesses — Anne Louise Bannon

Freddie and Kathy are happily enjoying their newly-married bliss when Freddie's sister, Honoria, finds a dead body in her apartment. Honoria had taken the young woman in as a favor to a friend but it soon becomes clear that the favor caught up. Honoria goes into hiding and Freddie and Kathy take up a chase that will lead all three of them across the country and into a conspiracy that, no matter how unbelievable, could get them all killed.