Unman, Wittering and Zigo

John Ebony (David Hemmings) is a former advertising executive who dreams of a nobler vocation: teaching. When assigned to work at a dodgy public school, he's initially eager to educate its troubled students -- until they inform him they murdered his predecessor. Fearful for his life, Ebony agrees to keep their crime secret. Once he discovers that the principal (Douglas Wilmer) plans to fire him at year's end, however, Ebony decides it is time to rewrite the terms of his extortion.