In Book Five, Katie Mingles With MI5, Katie and Bethany try to kick-start their detective agency again. Katie is settled, and in love with Marco, husband number three, or five, depending on how you count these things, and has no intention of mingling into her husband's world of MI5.
Having been accidentally hooked, there is no turning back as she enters the world of lies, sexpionage, and women's power over men's feeble minds.