Using the knowledge gleaned in the later books, I re-visited this one to understand what was really going on.
From what I can tell, the Black Council's goal was to waylay Mab's future plans involving Marcone & weaken the Unseelie Accords. However I find the reasons why Nicodemus & Titania want to be involved in this book puzzling.
Why does Nic go along with this plan? I understand that he feels that he needs to get back at Marcone for the "insult" given to him in Death Masks, & I'm sure having a Signatory to the Accords under his influence are important to him, but are these really enough for him to work with Tessa again, and go to "corporate" for support with the greater circle? We know that Nic hasn't worked with Tessa for nearly 700 years, is this really important enough for that?
I find it hard to believe that the plan to capture Marcone was expressly set up to capture the Archive - I believe this was opportunistic. The Denarians had no way of knowing that (a) Mab would use Harry in this case (likely since it was in Chicago, but Nic/ Anduriel would know that Harry hates Marcone) or (b) Even if Mab involves Harry, that he would reach out to Ivy instead of the White Council to mediate this dispute. Even if Harry doesn't trust the Council, he trusts Ebenezer, Rashid & probably Injun Joe & Luccio as well. Its possible that Nic & Anduriel had been spying on Harry enough to conjecture that he would call on Ivy, but the question becomes, why now? Why not go after Ivy when she was even younger & less able to defend herself?
The only explanation I can come up with is that Nic wants to know if Mab is Nfected, insane or weak. In Skin Game we see that Nic has a cause he is seemingly devoted to (perhaps fighting Nemesis in his own way) - if knows the true purpose of the Winter Court (guard the Gates), and he is hearing on the supernatural grapevine that Mab may be crazy, perhaps he cares enough to invest some real effort in finding this out. I wouldn't be surprised if this is what Tessa used to convince him to join.
Why does Titania oppose Mab in this instance?From what I can understand, the Summer Court exists to keep the Winter Court in check - i.e. make sure they are not distracted by matters not pertinent to guarding the Gates & in doing so, sparing most of the world from Winter's cruelty. By sending Harry to rescue Marcone, Mab is simply trying to enforce her own Accords, which I'm assuming Summer is also a Signatory of - so why would Titania send the Gruffs to stop Harry from being able to do this?
In the only hint of an explanation we see is in Cold Days where Titania is shown to be ridiculously angry with Harry - she says that without Eldest Gruff's counsel (whom Harry met at the very end of the book), she would not have moved on at all. So perhaps this was her focusing her wrath upon Harry before Eldest Gruff is able to calm her down.
The Black Council's plan is a little easier to fathom -
- Kidnap Marcone - ruin Mab's future plans
- The Black Council/ Maeve learn that Mab has big plans for the newly created Baron of Chicago & use their allies in the Denarians to abduct him, putting extreme effort into bypassing Marcone's security. I would not be surprised if the Denarians' plan was to give the captured Marcone an Nfected coin, or just kill him to remove him from play
- As we see in Skin Game, Mab has plotted for years to find a way to get the weapons in Hades' vault. The way she chooses is to support Marcone's bank for the supernatural, which accomplishes 2 goals - it severely punishes Nic for screwing with the Accords & it gains her entry into Hades' vault so Harry can retrieve the 5 artifacts/ weapons. Marcone is crucial to this plan working.
- Kidnap Marcone - weaken the Unseelie Accords
- The overarching plot of the series so far is that Nemesis is attempting to take over by breaking the supernatural alliances that keep the various powers from fighting each other in self-destructive wars. The way it chooses to do so is by weakening the Unseelie Accords, which were sponsored by the Winter Court - meaning that unless Winter is able to enforce the terms of the Accords, why should anyone obey?
- The seeming inability of Mab to go after the Red Court for violating her own passages is the plot of Proven Guilty - this signals to all the other powers that Mab may not be as strong as she was when the Accords were signed. We see that by White Night even the likes of Lara Raith are testing the Unseelie Accords (Harry points out that Lara had kidnapped a bunch of little folk to deliberately give the Winter Court a minor insult to see what they would do - which is nothing, since Mab has more important things to worry about)
- The Black Council uses its agents in the Denarians to convince them to kidnap Marcone. As I mentioned above, I believe Ivy's involvement was simply a bonus. If Mab is unable to stop 1 Signatory from simply grabbing another, it would signal to the rest of the supernatural world that the Accords were no longer in being adhered to, & with the White Council fighting an expensive war of attrition, everyone was fair play.