In 1941, a Lithuanian man kills his neighbor Jew, Isaac, at the Lietukis garage massacre. Twenty five years later in Soviet Lithuania, movie director Gediminas Gutauskas returns from the USA with a screenplay of a film that portrays, in details, the Lietukis garage massacre and describes a particular situation where Isaac, the Jew, is killed. The screenplay is later brought to the attention and investigated by the KGB. Why does a director, who once relocated to the USA, return to Soviet Lithuania? Why is his scenario so unusually historically accurate to the massacre, as though he would have witnessed it himself? Perhaps he knows someone who attended the massacre themselves? The aftermath of the murder returns many years later to cripple life and love. ISAAC is a trip into the past, and its rotting world, based on the neighbor Isaac's rotten murder.