Biggles, Algy and Ginger have volunteered to help, and fly reconnaissance missions over the country on the lookout for Soviet troops and aircraft. Quite by chance on one such flight, Biggles spots a lone figure at death's door in the snow, and lands to investigate. The man is Petolski, a Polish scientist. His plane crashed on the Finland-Russia border while he was trying to escape Occupied Poland with seven years' worth of experimental aircraft research. Rather than let it fall into enemy hands, he hashidden it somewhere near the downed plane.