Caprona was for Ed Burroughs what Mysterious Island was for Jules Verne: a place where the weird and impossible occurred. Burroughs' mysterious island is located in the cold waters of the far southern reaches of the Pacific Ocean, continually shrouded by fogs. The coast of this large island is protected by barrier cliffs, all but impossible to cross except by the most determined adventurers.

Caprona, named for an Italian circumnavigator of the previous century, has magnetic properties which render compasses useless. There is only one small pepple-strewn beach, and that is not far from a curious, warm, freshwatercurrent which seems to originate from the island itself!

Part one of The Land That Time Forgot relates how Bowen Tyler assumes command of a captured German U-boat crewed by the survivors of an English tug and the German submariners. This command is undermined by sabotage and the ever present danger that the Germans might try to retake their vessel. The saboteur secretly alters the U-boat's course at every opportunity until the underwater craft is far from all shipping lanes and deep into the waters of the south Pacific. Low on fuel with no chance to return to any port, the sitution is grave. Rising out of the cold mists is Caprona and Bowen Tyler takes the submarine beneath the barrier wall through an subterranean river. When the submarine surfaces in the island's interior, they are afloat on a massive waterway teeming with a profusion of life that is mind-numbing.

Almost immediately the reluctant adventurers are set upon by huge reptilian creatures which have been extinct for millions of years in the outer world. It is a place where evolution has taken an odd turn as only the grand master of adventure could write. All kinds of bizarre and prehistoric animals abound, as well as aquatic monsters and gigantic flying reptiles. Curiously, however, as Tyler's group travels up the river to the opposite side of Caprona, they move into lands where the jungles become parklands and the fierce reptiles give way to predatory mammals and deer-like horses. The greater the distance of the mouth of the subterranean river, the more evolutionary advanced are the flora and fauna, as if instead of traversing miles they are traversing the epochs. Tyler's group eventually encounters apes, ape-like creatures, and man.

Declaring a truce between the Germans and the English, all parties agree to work together until they are free of Caprona, yet external forces of such unusual nature, and the complication of a romantic triangle between Bowen, Lys, and the U-boat commander, puts a strain upon the agreed peace. The dangers of Caspak beseige the party and, as they say, things go from bad to worse!

When The Land That Time Forgot was written World War I was full-blown in Europe. The United States had not yet entered the war, though the sinking of the Luisitania (the inspiration for Bowen Tyler's adventure) had aroused the nation. The war machines then in use, the submarines, ships, and airplanes, are found in the three novellas which comprise the Caspak series.

The People That Time Forgot, begins in America. An expedition is gathered to rescue Bowen and Lys--their message in a bottle had been delivered to the Tyler home in California. Leading the expedition is Tom Billings, a long-time employee and family friend. A ship is outfitted and sails to the cold waters of the southern Pacific. In time Caspak is located and Billings flies over the barrier cliffs without difficulty, but is immediately set upon by a monsterous flying creature. The plane is wrecked, and from that moment on Tom Billings discovers the incredible savagry of Caspak.

Book three, Out of Time's Abyss, chronicles the tale of John Bradley and a handful of men from the English tug crew which had taken over the German U-boat. Fierce and primitive creatures make their exploration of the area near Fort Dinosaur extremely dangerous. Bradley becomes separated from his men and later finds himself upon the large island at the northern end of the immense inland lake. His adventures among the Wieroo, winged humans, and the events thereafter, reveal the true nature of evolution in Caspak.

The Caspak Series

	THE LAND THAT TIME FORGOT In 1916, survivors of a U-boat attack take command of a German submarine and enter into an adventure in a mysterious land where primitive creatures abound.
	THE PEOPLE THAT TIME FORGOT A rescue mission mounted to save Bowen Tyler encounters extreme difficulty with the monsters of Caspak.
	OUT OF TIME'S ABYSS Englishman John Bradley, separated from the original group of survivors, faces death many times over on the island of Weiroos.
	THE LAND THAT TIME FORGOT (omnibus) Contains all three parts listed above.