First, some quick backstory - The Nightside is the place where people (and non-people, for that matter) go to indulge their every twisted delight. It's the place where sin rules and its denizens love the freedom to do whatever they want, and they'll fight to the death to keep it that way. On the flipside, the Droods stand for everything opposite The Nightside. Rules, regulations, doing what they see as right. And they are more than happy to enforce their beliefs on everyone they can. However, both sides signed the ancient Pacts and Agreements eons ago that allows them to operate separately, within their own domains. But then something happened.
Night Fall begins with The Nightside inexplicably expanding its borders with horrendous consequences. The Matriarch of the Drood family summons Eddied Drood and his girlfriend, Molly Metcalf, the wild witch of the woods, to enter The Nightside and investigate, but according to the ancient Pacts and Agreements, Droods aren't allowed to set foot in The Nightside, which makes matters more difficult.
Naturally, Eddie dons his classic alter-ego, Shaman Bond, and everyone already knows Molly in The Nightside, so off they go. Unfortunately, their old haunt, The Wulfshead Bar, is under siege and friends are dying, so Eddie must bust out the golden Drood armour to quell the attack, clearly identifying him as a Drood violating the Pacts. This causes John Taylor, Walker and peacekeeper of The Nightside, to arrive at Drood Hall for a "chat" (another breach of the Pacts) and it just goes on from there, back and forth.
Before you know it, the Matriarch decides that the only way to end this mess is to invade The Nightside by dropping the entire Drood Hall right in the thick of it, complete with the entire family ready to go to war, and hopefully they can affect a mostly bloodless coup. Nothing goes according to plan, however. Soon, The Nightside begins to affect the Droods (as it affects everyone who dares to enter), and their bloodlust is in full gear, with Cedric, the Sarjeant-at-Arms, going full tilt war machine and determined to mow down everything and everyone is his path.
Bodies start dropping at an alarming rate, especially since the residents of The Nightside are fully fighting back, but Eddie and Molly are just trying to get to the bottom of the mystery of The Nightside's expanding borders while there are folks still alive on both sides. In digging, they discover an alarming plot, and leaders on both sides will have to do shocking things in an attempt to win. Expect to see lots of familiar faces on both sides to join the battle. Can Eddie and Molly work with John Taylor, and his wife, Shotgun Suzie, to bring this war to an end or will both sides destroy themselves in the process?
Night Fall is a good end to the Secret Histories series and seems to be a good one to close the book on The Nightside as well. Lots of characters perish on both sides, but of course, having not read The Nightside series, I didn't know these characters well enough to impact me. Your mileage may vary - some seem pretty harsh. Either way, Night Fall is a great way to for Simon Green to cap off both series. If you've been reading them so far, you'll want to see how it all ends.