Kevin Costner and Jon Baird joined Greta Van Susteren tonight to discuss their new book, "The Explorers Guild."

They explained that the adventure is set against the backdrop of World War I. The Explorers Guild, a clandestine group of adventurers, go on a quest to find Shambhala, the golden city of Buddhist myth.

"The idea was to go back in time," Costner said, explaining that they wanted to stand on the shoulders of authors they love, including Rudyard Kipling, Jules Verne and Mark Twain.

"This represents about four years of just putting your nose down, Jon specifically, and just going after that," Costner said.

Watch more above.

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