The Dakota cipher

"With President Thomas Jefferson's blessings, Ethan and Magnus embark upon an expedition into the western wilderness--keeping their eyes open for woolly mammoths. But another prize secretly impels them : the mythical hammer of the Norse god Thor, allegedly carried to North America more than a century before Columbus. Across a landscape no white man has ever traversed, Gage's skills will be tested as never before--as he bravesunimaginable peril en route to the most incredible discovery of all time." [back cover]