The Charlemagne pursuit

Ex-agent Cotton Malone wants to know what really happened to his father, officially lost at sea when his submarine went down in the north Atlantic. But when he uses his government contacts to obtain the submarine's sealed file, Malone finds he is not the only person looking for answers. Pitched into a lethal power struggle between mysterious twin sisters Dorothea Lindauer and Christl Falk, Malone embarks on a dangerous adventure involving Nazi explorations in Antarctica, US government conspiracies, and a series of cryptic clues built into the legend of Charlemagne. Forced to choose a side where neither can win, Malone is determined to uncover the truth behind his father's death - but can he escape his own? [okł.]