Amazon.com Product Description (ISBN 141691918X, Mass Market Paperback)

Buffy thought she'd finished the Master when she dusted him. But in Sunnydale things have a way of coming back. . . . The Master may be dead, but he is not forgotten. One of the vampire lord's devotees sets out to alter the past so that he can resurrect the Master without Buffy's meddling. When he conjures up a portal to transport his minions through time, the vampires are poised to murder the most powerful slayers in history!

It is up to the Scoobies to stop the Master's followers before they break the chain of slayers. Giles, Xander, Willow, and Buffy pursue the vamps back in time through the portal to save the slayers of the past. They must track the bloodsuckers from the French Revolution to the American Civil War without getting detected -- or worse!

But you can't change the past without changing the present. . . .