The Vulgar Heart by Mary Lancaster

When convention clashes with love…
Eager to outshine her older sisters, Henrietta Maybury is disappointed to discover the first man to make her heart race is the scion of a banking family, and therefore quite ineligible as a husband to a viscount’s daughter.
But as it turns out, Captain Sydney Cromarty is even less marriageable than she first imagined. For beneath his respectable facade, he’s a notorious smuggler – as Henrietta discovers during a reckless evening at the Hart Inn. And the more she learns, the more he fascinates her.
As Henrietta begins to doubt her values, Cromarty is forced to reassess his own. No one is more amused than he to discover he is now the Earl of Silford’s heir, a position he has no intention of embracing, but it becomes a situation that makes him dangerous enemies who are not above using his growing feelings for the charming Henrietta to destroy him.
Will he accept his patrimony as a means to win Henrietta, or will they both succumb to the threats that surround them?