Shadow World by Ray Cummings

From The Lost Sci-Fi Podcast - Vintage Sci-Fi Short Stories Scott Miller

Two men cross into a mysterious fourth-dimensional world in search of a rare element that could save their own civilization — or destroy another. But the moment they arrive, they discover they are not the only ones with a hidden agenda… and not everyone plans to return alive. Shadow World by Ray Cummings. That’s next on The Lost Sci-Fi Podcast.