Crown of Mist (Culloden’s Fire Book 4) by Kimberly Cates

An Irish Patriot...
When Cromwell’s army invades Ireland, swordswoman Brianna Devlin defies her brothers and goes to fight beside them. As Drogheda falls, she crosses swords with an English lord as desperate to escape as she is.

A Cavalier Spy...
Lord Creighton Wakefield joined Cromwell's army to gather intelligence for his childhood friend who will one day be Charles II, but his mission has been discovered. Wounded, he tries to flee the city with valuable information—but is stopped by a sword-wielding beauty who means to take him down as one of Cromwell's men.
An Unlikely Ally…
Creigh realizes his best chance of escape lies with the Irish tigress and convinces her to join forces. As Creigh and Brianna race toward the coast and freedom, the tides of civil war sweep them from Ireland to the dungeons of the Tower of London, then to the treacherous exiled court in France, where they find a sword filled with magic and discover that the most dangerous risk they can take is to love each other.

Culloden's Fire series:

1. GATHER THE STARS (Gavin and Rachel)
2. ANGEL'S FALL (Adam and Juliet)
3. CROWN OF DREAMS (Myles and Devlin)
4. CROWN OF MIST (Creighton and Brianna) Prequel

Celtic Rogues series:

1. BLACK FALCON'S LADY (first published as NIGHTWYLDE by Berkley Books)
(Tade and Maryssa)
2. HER MAGIC TOUCH (first published as MAGIC by Pocket Books)
(Ciaran and Fallon)
3. BRIAR ROSE (Lion and Rhiannon)
4. STEALING HEAVEN (Aidan and Norah)
5. LILY FAIR (Niall and Caitlin)