The Queen of Sinister (Dark Age #2)

The plague came without warning. Nothing could stop its progress: not
medicines, not prayer. The first sign of the disease is black spots
at the base of the fingers; an agonising death quickly follows. But
this is no ordinary disease ...Caitlin Shepherd, a lowly GP, is
allowed to cross the veil into the mystical Celtic Otherworld in
search of a cure; her search takes her on a quest to the end of a
land of dreams and nightmares to petition the gods. Caitlin is
humanity's last hope, but she carries a terrible burden: a
consciousness shattered into five distinct personalities ...and one
of them may not be human. THE QUEEN OF SINISTER is the latest
instalment in Mark Chadbourn's riveting 'Dark Age' sequence: a
masterful blend of Celtic myth and Arthurian legend in a modern
setting.