The Phantom Of Drury Lane by Kate Bateman

Intrepid Lucy Montgomery has survived a shipwreck off Madagascar and the sweltering jungles of Brazil, but now she’s finally back in London she has something worse to deal with – her long-time nemesis Will Arden, Viscount Wade.
Their one, impulsive kiss five years ago led to her humiliating rejection, so the fact that she’s never been able to forget the handsome scoundrel is vexing indeed.
When Arden challenges her to uncover the identity of the mysterious Phantom of Drury Lane, Lucy can’t say no—but her snooping might just push them both past the point of no return . .