Think of a Number (1969)

The story opens just before Christmas, when solitary, apathetic bank clerk Flemming Borck uncovers a plot to rob his bank. After doing a little rookie recon, Borck identifies the would-be bank robber as a faux shopping-mall Santa Claus, and counter-plots to steal the money himself and let Santa take the blame. This works out about as badly as you might imagine, and our bumbling protagonist spirals further and further away from the carefree, laconic lifestyle he had hoped to ensure for himself.