Night Vision by Karin Kallmaker

Julia Madison is having nightmares. Every night. All night. Painful and perplexing, the nightmares of a woman in captivity calling for help escalate until she is having them during the day, wide awake. Doctors prescribe pills. Therapists theorize about past lives and post-traumatic stress. Fortune tellers predict she will meet a tall, mysterious stranger. Julia would prefer to blame her ex, her job, even the Santa Ana winds. In spite of her long history as a loner, she turns to a support group for women with sleep disorders. To her amazement she learns that the other lesbians in the group--and only the lesbians--are having similar nightmares. No longer believing these vivid night visions are in their heads, the women join forces to find the source of their disturbance. Since Julia knows that her dreams focus on the woman she's named Sirena, finding Sirena is her number one priority. Convincing the other lesbians to help her comb the Mojave Desert is only the beginning of the adventure.