The Devil's Saturnalia - Hellbound, #6

While in Scotland for Lionel's magic training with Hades, a murder case compels the Devil and his necromancer to stick around a little longer. Lionel, who still cannot control his demigod magic properly, doesn't mind a murder investigation, because that is something a necromantic police consultant like himself knows how to handle. Except, the investigation doesn't go at all as Lionel thought it would.
And when he decides he wants to open up to Lucifer, finally, that doesn't go exactly as Lionel had feared either, but some surprises are good surprises, especially when Saturnalia is just around the corner. Lucifer is delighted. He has his boyfriend, who finally opens up, and his boyfriend is all his, at least through the holidays. That much attention is exactly what Lucifer loves, and the holiday season would be entirely perfect -- if it weren't for an old enemy who is out for vengeance.