The Empty Grave
Jonathan Stroud
The climactic conclusion
The fifth paragraph of Jonathan Stroud's The Empty Grave begins thus
You know how it ended. Everyone does. The city was already full of it on that last cruel morning, ...
and then goes on to hint at some of the grand events to come.
Of course, you DON'T know how it ended. That's just Stroud teasing you. And I won't spoil it. You do, however, know some of the secrets that Lucy's London doesn't, because you have read The Creeping Shadow. The Empty Grave is not a standalone book -- I will assume you've read the four previous Lockwood & Co books. If you haven't, there will be spoilers!
To wit, in The Creeping Shadow we learned that the unquiet dead inhabit a parallel world, and that sources (which is what, in the world of Lockwood & Co we call the objects that allow ghosts to appear in the living world) create portals from the living world to the dead world. It is possible for a person to pass into the world of the dead through such a portal and come back alive. Furthermore, the two largest ghost-hunting agencies, agencies, Fittes and Rothwell, have been doing just that.
As an unintended result of the Lockwood Agency's investigation Rothwell's Agency has collapsed and been taken over by Fittes. Fittes is now threatening to take over all psychic investigation. Penelope Fittes has literally threatened Lockwood & Co and has ordered them to cease all major investigation of The Problem.
Yeah, right! How do you suppose Lockwood and Co respond to that? Penelope Fittes (or the entity currently posing as Penelope Fittes) is many things, but she is not a fool. She knows as well as you do what kind of obedience she can expect from Lockwood & Co.
And thus a confrontation ensues leading to the events of "that cruel morning" that Lucy hints at. It's a good story.
One of the most difficult things for an author, apparently, is finishing. I love Seanan McGuire, but I would love her more if there were any evidence that she can finish a long story. Stroud has proved that he can close a deal. And never better than in Lockwood & Co.