Return to the Hollow Earth is Rucker's second steampunk novel featuring Mason Reynolds. In 1850, Mason and his wife Seela embark upon a perilous trip around Cape Horn to San Francisco. Their ship sinks, but they're saved by a tentacled, flying nautilus--who carries them to meet Edgar Allan Poe. Poe leads them on a return voyage to the Hollow Earth, passing through the throat of a thousand-mile-deep maelstrom at the North Pole. Within the Hollow Earth, they learn that the god-like woomo sea cucumbers mean to send them them on a epic mission across space and time. The initial stage of this mission brings them to Santa Cruz, California--in the year 2018. And then things get gnarly.