Willie Fowlie's grandmother calls him a 'nickum' - he is a mischievous Aberdeenshire boy who often acts instinctively, bearing little or no consideration for the consequences of his actions. When he is eleven, his playful antics lead to a full-blown murder enquiry, but it is soon recognised that the hunt is based on nothing more material than Willie's imagination. Four years later, however, Willie witnesses a real murder, but believing that his eye-witness testimony is simply another fabrication, the police wind down the investigation. It is not until five years later, during World War II, that Willie is able to prove the sincerity of his account and the murderer is apprehended.Despite his errant ways, Willie's headmaster recognises his potential and finances his matriculation at University along with his own daughter, Millie, in late September 1939. Free from the constraints of their childhood, the blossoming of their love begins to unfold. However, within weeks of the outbreak of war, Willie's best friend from childhood enlists in the army, but Willie feels duty-bound to his sponsor to obtain his degree.
Two years later, however, in 1941, Willie is confronted with the news that his friend has been killed in action. Racked with guilt, blaming himself for not being there to protect him, Willie abandons his education and volunteers for the Gordon Highlanders. The course of his life is now completely changed, the troubled boy that he was now a distant memory, but can the 'nickum' ever atone for the decisions that he has made?