Picking up directly from the events at the end of Shockscape, Ryan Cawdor, his son Dean, Krysty Wroth, J.B. Dix, Dr. Theophilus Tanner, Mildred Wyeth, and Michael Brother find themselves trapped at the exterior entrance of a redoubt somewhere south of Yuma, Colorado.

Ryan makes the decision to scale the mountain the redoubt is built into, with the intent of reaching a section of corridor which has been opened to the elements following an earthquake.

He then makes his way into the redoubt, carefully moving past a hive of mutated albino worms, previously shown to be carnivorous and capable of burrowing through solid concrete.

The companions exit through a partially submerged, open tunnel, finding themselves on a chain of islands; using his sextant, J.B. places them on the Florida Keys.

The companions venture south, and eventually come across a seemingly intact facility identified as the Mark Tomwun Institute of Peaceful Oceanographic Research.

Later on an Institute trip to observe ocean phenomena, Ryan is tipped overboard by an undersea volcanic eruption, and washes ashore a large distance from the rest of the group.

He assures Ryan that the sinking was a mistake, and the intended target was the man who he asserts slaughtered the crew: Red Jack Yoville, leader of a large band of pirates.

Disgusted with Tomwun's tactics and relative apathy over the deaths of the Seminole merchants, Ryan still agrees to spare his life and the lives of the Institute's other occupants; the companions leave for the redoubt the next morning.

Scouting missions during the first four days reveal nothing, save for a peculiar race of mutants living in a near-immaculate Best Western hotel on a southern island.

The next day at dawn the pirates attack en masse, coming over land with war wags and armed men as well as by boat from the north and south.

Before entering the still-submerged entrance the group noted the source of the earthquake: a visible and gigantic volcanic eruption roughly 50 miles from shore.