The principal character is a young Scottish pilot with bush-flying experience in Canada, Donald Ross, who is hired by an Oxford don, Lockwood, to pilot an air survey mission of Greenland. Lockwood's interest is in the early Viking seafarers and their exploits and although he appears to have little knowledge of the needs of such a project, he insists on their starting as soon as his elder brother, a businessman, can provide finance.
Ross, as the hired expert, then has to contend with the 'helpful' suggestions from both the financier and Lockwood's young daughter, Alix. This causes early tensions in the preparatory stages.
While the preliminary dig is ongoing Ross shoulders much responsibility including keeping the aircraft safe in a tidal zone. Worn out with the work he becomes ill, and in a fever dreams that he and Alix were once Scottish slaves aboard Leif Erickson's vessel on its voyage of discovery. A part of this dream includes a stone with their names carved on it left behind in America.
Ross recovers and tells Alix of his dreams. The project is, ultimately, a success, and they cross to America. Flying down the coast Ross recognizes where he dreamed the Norseman landed on the coast of Cape Cod, and investigating, finds the stone with the slaves names on it.
The technical details of a trans-Atlantic flight of this period (late 1930s) are accurate and of interest. The type of aircraft is not specified beyond being of American manufacture for bushplane use. It corresponds roughly to the performance of a Noorduyn Norseman.
This was Shute's first attempt at re-incarnation as a plot, a second later work on this theme is In the Wet.