Some movie posters for this film featured a long text preamble that read: "At 29, Charles Heller was a mathematician without equal. At the CIA, he was a computer expert without peer. But when terrorists murdered the most important woman in his life, he became an assassin without experience. To avenge her death, the CIA trained him, briefed him, armed him, and then...they abandoned him. The first 11 minutes will absolutely shock you. The last 11 minutes will rivet you to your seat. The Amateur".
The film's writer is Robert Littell who is a journalist and novelist who specializes in espionage novels that frequently are set around the spy world of the CIA and the former Soviet Union. He wrote the screenplay for this movie then wrote the novel of the same name after-wards. The book has a slightly different title, it being "The Amateur: A Novel of Revenge (1981)". This film was his first film & TV credit.
The trivia item below may give away important plot points.
The film's closing epilogue states: "Sam Kaplan retrieved the information from the Astro Computer in the diner and sent it to Heller. Heller's book was published one year later. Heller and Elisabeth Vaculik are living under assumed names. Their whereabouts are unknown".