A double post, but it's been the better part of three months, so...
Idea: After the latest novel, Harry goes to Mac's for a cold beer and to catch up with old friends. After he gets a few beers in him, he mentions how sad Mab no doubt feels over the loss of her daughters, and how he feels so inadequate since he can't see any way to fix it. Then someone (Michael Carpenter? Sanya?) suggests that he get into a sexual relationship with both Mab and Sarissa, so that they'll have an excuse to spend time together. In his intoxicated state (and with the Winter Knight mantle amping up his sex drive), he thinks that this is a smashing idea, and promptly heads back to the Nevernever to relay this idea to Mab.
After waking up in Mab's bed the next day, she reminds him of this idea, and so he sets out to the Summer Court, knowing that failing will make Mab sad (and he really doesn't like the idea of making women sad, he's chivalrous like that), but also not liking that it'll put pressure on her to accept (since he's chivalrous like that). Being a smart cookie, however, Sarissa tells him that he'll have to court her, like a proper knight. And when Titania finds out about it, she makes him compete against Kit to accomplish various near-impossible tasks.
Hilarious harem antics ensue, as Molly and Murphy wind up getting involved in this as well. After all, if he's going to be in a relationship with more than one woman, there's no need to limit himself to just two, now is there?