The Caspak trilogy is fantasy novel by Edgar Rice Burroughs, it is consisted of 3 works:
The Land That Time Forgot is an Edgar Rice Burroughs fantasy novel, the first of his Caspak trilogy. The novel is set in World War I and opens with a framing story in which a manuscript relating the main story is recovered from a thermos off the coast of Greenland. It purports to be the narrative of Bowen J. Tyler, an American passenger with his Airedale terrier Nobs on a ship sunk in the English Channel by a German U-boat, U-33, in 1916. He is rescued by a British tugboat with another survivor, Lys La Rue. The tug is also sunk, but its crew manages to capture the submarine when it surfaces. Unfortunately, all other British craft continue to regard the sub as an enemy, and they are unable to bring it to port. Sabotage to the navigation equipment sends the U-33 astray into the South Atlantic. The imprisoned German crew retakes the sub and begins a raiding cruise, only to be overcome again by the British. A saboteur continues to guide the sub off course, and by the time he is found out it is in Antarctic waters.
The People That Time Forgot is an Edgar Rice Burroughs fantasy novel, the second of his Caspak trilogy. The novel begins with the organization of an expedition to rescue Bowen J. Tyler, Lys La Rue, and the other castaways marooned on the large Antarctic island of Caprona, whose tropical interior, known to its inhabitants as Caspak, is home to prehistoric fauna of all eras. Tyler's recovered manuscript detailing their ordeal is delivered to his family, and the relief effort is put together by Tom Billings, secretary of the Tyler shipbuilding business. The expedition's ship, the Toreador, locates Caprona, and while the bulk of the crew attempts to scale the encircling cliffs Billings flies over them in an aircraft.
Out of Time’s Abyss is an Edgar Rice Burroughs fantasy-science fiction novel, the third of his Caspak trilogy. The book begins with Bradley, who had left Fort Dinosaur on an expedition in the first novel and never returned. Bradley and his party are attempting to return to Fort Dinosaur. Along the way, they encounter a creature which appears to be a flying dead man. Some of the members of the party consider it to be a ghost or banshee. Tippet is convinced that he is soon to die, and the next day he is killed by a Tyrannosaurus. The ghost-like creature is seen again, and James is killed by a saber-toothed cat. Bradley disappears during the night, and the remaining members of the party make it safely to Fort Dinosaur.