A family drama encompassing both world wars. Having earned a medal at the Battle of the Somme in 1916, Sergeant Mark Bayley, 4th Hussars, is posted back to England and volunteers for the Royal Flying Corps, becoming an ace with 23 'kills' to his credit, before being shot down over the German lines in March 1918. While in a prison hospital he falls in love with German nurse Karolina von Bitterman. They marry after the war, but Mark's apparently idyllic life carries a shadow. During embarkation leave in 1917, he had enjoyed a brief but ultimately catastrophic affair with an Englishwoman, and suddenly finds himself responsible for her orphaned son. Karolina willingly adopts the child, although she has a son of her own by Mark. As long as she lives there is harmony. But following her tragically early death from cancer in 1934, the family falls apart.

The two boys, as sons of a famous airman, are naturally destined for the RAF, but while John, the son of the English mother, passes through Cranwell and into the service, Karolina's son, Max, allows himself to be seduced, by an unscrupulous German cousin, into returning to the Fatherland, where he renounces his British citizenship and joins the Luftwaffe. Thus, when war breaks out, in 1939, the two brothers find themselves on opposing sides.