This is book number 3 in the Lady Helen Trilogy series.
The thrilling, genre-bending conclusion to the Dark Days trilogy
Bath, 1812. As Lady Helen prepares for her grand wedding to the Duke of Selburn, she must juggle her new responsibilities with her duties as a demon-hunting Grand Reclaimer. Now a dyad with Lord Carlston, bonded in blood, the two prepare to confront their nemesis, the Grand Deceiver. Set against the glittering background of Regency society, Helen and Carlston's story hurtles to a shocking conclusion full of passion, betrayal, and heartbreak.