After Glow by Jayne Castle (a.k.a. Jayne Ann Krentz)

Life is complicated for Lydia Smith. She’s working at a tacky, third-rate museum, Shrimpton’s House of Ancient Horrors, trying to salvage her career in para-archaeology—and dating the most dangerous man in town. Just when she thinks she might be getting things under control, she stumbles over a dead body and discovers that her lover has a secret past that could get him killed. Just to top it off, there’s trouble brewing underground in the eerie, glowing green passageways of the Dead City.