The Dakota Cipher — William Dietrich

Ethan Gage wants to enjoy the fruits of victory after helping Napoleon win the Battle of Marengo. But an ill-advised tryst with Bonaparte's married sister has made that impossible. And the fantastic schemes of the wild Norwegian Magnus Bloodhammer soon have Ethan dodging hostile Indians on America's frontier.

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 braves unimaginable peril en route to the most incredible discovery of all time.