Directed by Michael Winner, who was extremely prolific at this point in his career, between 1970 and 1973, he directed a whopping 7 films, all of varying quality. Here, Winner was offered this thriller written by playwright Lewis John Carlino, who had originally wrote it as a novel, before it was optioned as a film by United Artists. It's actually a good thriller, and it shows Winner could do well with the right material. Arthur Bishop (Charles Bronson) is an assassin who works for a top secret organisation, and he's what's known in the killing trade as a "mechanic", who has a sophisticated and complex approach to his hits, he takes time to set them up, covering his tracks well. But, the job brings great stress, and Bishop suffers a blackout as a result. After being assigned to kill one of the organisations heads, Big Harry McKenna (Keenan Wynn), he later meets Big Harry's son Steve (Jan-Michael Vincent), who is intrigued by what Bishop does for a living, and Bishop thinks Steve has the perfect personality for a hitman, and makes Steve his apprentice. It's a very serious action film, but while Winner is known for cutting corners, making his films look shoddily made, this one is meticulously made, rather like the hits set up by Bronson in the film. It's actually the best collaboration between Bronson and Winner, well made and compelling, even though it was remade in 2011 by Simon West.