In The Miocene Arrow Sean McMullen returns to the post-apocalyptic setting of his previous novel, Souls in the Great Machine.

He does not, however, return to the same location, Australica. The Miocene Arrow takes place two decades after the events of Souls in the Great Machine and on the continent of North America.

Like Australica, North America is subject to the Call that compels any creature to walk mindlessly toward its source. Only birds and animals the size of a terrier or smaller are exempt from its lure. There are Havens where the Call comes periodically rather than constantly, and of the three in North America, Mounthaven lies in the former United States.

Mounthaven is divided into a system of kingdoms governed by an elaborate hierarchy of airlords, governors and wardens, and tied to a strict chivalric code. Ground war is a thing of the past; rather, ritual air combat settles differences, either as a one-on-one duel or using an airlord's fleet, and the impact on the common populace is minimal.

All that starts to change, however, as Mounthaven is infiltrated by aviads from Australica, members of a radical anti-human group. Genetically able to resist the Call, they are able to wreak havoc and pit kingdom against kingdom, throwing out the code of chivalry. Their ultimate plan is to release the Miocene Arrow, a weapon which will ensure their dominion. The weapon is chilling in its simplicity, particularly in the face of the complex aviad scheme.

They aren't the only ones infiltrating Mounthaven. Theresla, the mouse-nibbling abbess, Darien, the silent scribe, and the robust and randy John Glasken from Souls are also present, working desperately to turn the tide against the aviads.

The rich and complex plot is mind-boggling at first, and the going can be slow until the characters and events get sorted out. Once that happens -- and it doesn't take too long -- the narrative takes off at a rip-roaring breathtaking pace. The action breaks from one of the various subplots to another, raising the pitch of the suspense and keeping the reader turning pages. The characters are well-developed and convincing, engaging the reader's emotions without manipulating them. The novel is not without humor -- usually involving Glasken's antics -- which leavens the serious tone and adds dimension to the plot.

McMullen revealed the creatures producing the Call in Souls of the Great Machine, and in The Miocene Arrow, he gives the reader the story behind the Call and its creatures. In part, the story is a cautionary tale in that it was almost literally a careless thought which set off the chain of events.

The Miocene Arrow is at once fast-paced and thoughtful, a testament to McMullen's skill and powerful imagination. It is possible to read it without having read Souls, but I encourage you to treat yourself to both books -- they are definitely worth it.