Books in the Hours of the Night series

It's Mardi Gras, cher, but this year le bon temps kick off with murder…For generations, the White Monks have treated the vampire Thaddeus Dupont as a weapon in their battle against demons. However, when a prominent matron drops dead at a party, Thaddeus and his lover Sarasija are asked to find her killer. Their investigation leads them to an old southern family with connections everywhere: Louisiana politics, big business, the Church, and an organization just as secret as the White Monks. Meanwhile, an esoteric text containing spells for demon-summoning has disappeared, Thaddeus is losing control of le monstre, and Sara is troubled by disturbing dreams. These nightmares could be a side-effect of dating a vampire, or they could be a remnant of his brush with evil. As the nights wear on, Sara fears they are a manifestation of something darker - a secret that could destroy his relationship with Thaddeus.