I think this is my favorite of the series so far, how I loved this story, how I felt cozy and emotional while reading it.
Devlin is the Mad Duke, the descendant from a powerful noble family of black witches, a practitioner of rune magic. Midnight is the Corpse Child, a draugr, who Devlin bound to his own life in order to save him after he was killed and give him a sort of life, feeling he failed to protect him. Devlin and Midnight share heart, breath and soul. Midnight has always loved Devlin, since the very first glimpse he had of the man, with his starving childish imagination seeing him as a sort of angel after an act of generosity. This imprinted itself in Midnight, making Devlin his treasure, the only person for whom the dead child came back to life. This was so incredibly creepy! Midnight is considered a sort of abomination or curiosity, the magic of his making a secret Devlin guards fiercely.
Even if Devlin took care of Midnight since when he was a child, their relationship has never been one of father and son. Devlin has always felt protective of Midnight, but his honor prevents him from acting on the attraction he feels for the grown-up Midnight and taking advantage of the young man's attraction to him. He is afraid that Midnight's attachment depends on the obsession a draugr develops for their loved one, and not on a real feeling. While Devlin would love for Midnight to lead a normal life, to love and be loved as a normal man, he also is jealous of him. Midnight wants to be treated as a man, not as a child, he wants his feelings to be acknowledged by Devlin for what they are, he wants to love and be loved by Devlin completely. He is afraid Devlin sees him as a corpse and is repulsed by him, and he's afraid that his limitations as a draugr make him an unsuitable partner for the duke.
So we have: a proud, arrogant but generous nobleman, who tried to right the unfair death of a child; a lovely, sweet young man, who has experienced and never forgotten a single act of kindness. It was sweet and heartbreaking and sweet again. The sex is not explicit, there's sensuality, the attraction between the two men is shown with a delicate touch that makes every touch and kiss precious.
I love the world the author built for this series, it gets richer with each installment. In this book, for example, there were some great secondary characters. Barra, the Duke's personal assistant, is a wolf-elf with a great taste for elegant clothes. He falls in love with the pair formed by the knight Neirin and his dragon Troyes. They provide the tension-breaking moments of the book.
The first half of the story is told in Devlin's point of view; the second half in Midnight's. Unlike the previous books of the series (which could all be read as stand-alones), this tells one long story and not episodes or single cases involving the main couple.
Recommended if you're looking for a potential comfort read.