I just did a quick google to site check. eHarlequin.com has these posted writing submission
guidelines for their Nocturne Bites line:
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Writing Guidelines[/SIZE][/FONT]
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Nocturne Bites[/SIZE][/FONT]
Length: 10,000—15,000 words
Senior Executive Editor: Tara Gavin
Associate Senior Editor: Ann Leslie Tuttle
Silhouette Nocturne books is looking to acquire paranormal editorial with strong sexual, fantasy and danger elements for its new eBook program, Nocturne Bites.
We’re looking for fast-paced novellas that hook the reader early on by establishing a paranormal world and its conflicts. We are looking for stories of vampires, shape-shifters, werewolves, psychic powers, etc. set in contemporary times.
Many of the elements that make a Silhouette Nocturne book successful remain true for the Nocturne Bites series. Stories should deliver a dark, highly sensual read that will entertain readers and take them from everyday life into an atmospheric, complex world filled with characters struggling with life and death issues. A strong alpha hero is of utmost importance—he should be powerful, mysterious and totally attractive to the heroine.
While action-packed and mission-oriented, the scope of these stories should be more contained, with additional focus placed on character development. All stories should be capable of standing alone; all loose ends need to be tied up, and the relationship between hero and heroine should resolve itself in a satisfying manner.
That said, they're pretty up front on what they want."...Alpha male...powerful, mysterious and totally attractive...characters struggling with life and death issues.."
If you are writing for yourself, and not for one of the mass market publication houses, just write it how you want. If your goal is getting in to Harlequin, read the guidelines first.