Ray Cummings: The Flame Breathers

Summary

Did the planet Vulcan exist? It supposedly orbited our sun on the opposite side from the Earth but it was only theoretical speculation. One expedition had mysteriously disappeared, and now another was following in its path—searching for the truth about this planet's existence. Was there really an unknown menace that stalked Vulcan's shadowed gorges? I can tell you now that there was indeed something terrifying and very dangerous. This was first published in Planet Stories March 1943.