Spying on My Scoundrel - Linked Across Time, #13

The prince of a small country visits London, and Lady Hyacinth declares she'll make him fall in love with her in less than a sennight. After all, she would make the perfect princess. Rhys Rossington, the Earl of Carrick works for the home office, and he's assigned to the prince while he's visiting. Some believe he is visiting for nefarious reasons and expect Rhys to uncover the truth. Rhys and Hyacinth both remain close to the prince, but neither one of them expect where it will lead them.
While they have openly disliked each other, whatever their differences are, sometimes love is stronger than hate. With danger lurking in the shadows, they must finally face their feelings-or risk never admitting what is truly inside their hearts.