Midnight Crystal. Number 9 in series

Adam Winters has enough responsibility as the new head of the local ghost hunters' guild without being saddled with the family curse. He's convinced his recent nightmares and hallucinations will lead to him becoming a psychic rogue - unless he can find a stolen relic and a woman who can read dreamlight. Marlowe Jones rides into his life on a motorcycle and, though a descendent of the rival Arcane family, she's just what Adam needs: a psychic private investigator and dreamlight reader extraordinaire.
Together, amid the glowing catacombs and steamy underground jungles of Harmony, Adam and Marlowe must break the curse, save the entire underworld - and fight a passion that could destroy them both.