Unseen

The Unseen trilogy consists of three books authored by Nancy Holder and Jeff Mariotte.

Unseen, Volume 1: The Burning

Salma de la Navidad, a friend of Willow's, is having problems: her brother Nicky has disappeared and is believed to be joining a local Sunnydale gang called the Latin Cobras. Salma's also got a black shadowy nothingness that Buffy can sense but can barely fight. Meanwhile in LA, Angel is tied down by a case where his client is wrongfully accused of murder by crooked cops while Cordelia discovers a pack of pre-teens who revere vampires and have been promised eternal life by a vampire. Buffy's work takes her to LA along with Willow to the de la Navidad household where the same black shadow continues to attack Salma. When Salma suddenly disappears as does Kayley (one of the vampire lovers) everyone knows that something is up. After an explosion of oil fields, caused by Nicky, in Sunnydale, Riley rushes to LA where himself, Buffy and Angel have to work together to solve the disappearances and to calm down the gang warfare going on in LA.

Unseen, Volume 2: Door To Alternity

In Los Angeles, Angel and Buffy compares notes and realize that both of them are dealing with cases of missing teenagers - most of them are children of the rich and powerful. Coincidence? They don't think so. But when Buffy checks in with Giles, she learns that prime time doomsday has hit Sunnydale, taking precedence over the gang warfare in LA. Back in Sunnydale, Buffy finds the gateway through which the monsters are gaining all access passes to our universe. These gateways are controlled by renegade scientists who have discovered how to manipulate time and dimensional portals from one reality to the next, which could explain where the teens are hidden. But something goes wrong and nothing ever comes out of these gateways the same way that they went in. Now they come out bent and destroyed. Alina is the only child that can control these portals but either she's lost her control or something in the Hellmouth is breaking these barriers. Buffy and Angel must go into the portal and see if they can salvage any of the children left on the inside.

Unseen, Volume 3: Long Way Home

Buffy and Angel have travelled into the dimensional portals in order to find the missing kids. Unbeknownst to them, Spike took a running leap and dived in after them. They all end up on the same plane but it totally different areas: Angel locates a girl in a forest, Spike ends up in a vampire zoo and Buffy ends up fighting a dragon near an enchanted castle. Their job is to locate the 50 of so kids that have gone missing lately. Meanwhile, back on Earth, Gunn is helping Riley to bust Faith out of jail in order to send her to the alternate planes as well. In Sunnydale, Giles and Xander are trying their best to keep the monsters at a bare minimum level. Once Buffy and co., have located the missing children, the problem becomes how to get them back...