From the back cover:
Forbidden maps... mysterious archaeological sites... ancient sunken shipwrecks...
Do history's secrets intrigue you while its inaccuracies repel? Do you bristle at excessive accolades that dilute a job well done? Do you delight in technological wonders and tea at four?
Welcome to the National Archaeological, Geographic, and Submarine Society! Terra Incognita is a roleplaying game of exploration, intrigue, and mystery, featuring adventure-scholars whose exploits span the late Nineteenth and early Twentieth Centuries. Armed with extensive training, unpredictable technology, and unimpeachable discretion, Society members ("Nags") travel to the Four Corners of the globe - exploring unknown lands, investigating mysteries, and uncovering ancient knowledge. The Society studies and catalogs the information and artifacts so gleaned - and sets about covering such things back up again if they deem the world is not yet ready for the knowledge or power that had lain hidden for so long.
So sharpen your Sword Cane, brush up on your Diplomacy skills, pack your Adventurous Attire, and join us in the exploration of Terra Incognita!