<P> The series follows the exploits of the Impossible Missions Force (IMF), a small team of secret agents used for covert missions against dictators, evil organizations and (primarily in later episodes) crime lords . On occasion, the IMF also mounts unsanctioned, private missions on behalf of its members . </P> <P> The identities of the higher echelons of the organization that oversees the IMF are never revealed . Only rare cryptic bits of information are ever provided during the life of the series, such as in the third season mission "Nicole", where the IMF leader states that his instructions come from "Division Seven". In the 1980s revival, it is suggested the IMF is an independent agency of the United States government . This is implied by the fact that towards the end of the taped instructed messages, the narrator includes the passage: - "As always, should you or any of your IM force be caught or killed, the Secretary will disavow any knowledge of your actions", or words to that effect . </P> <P> The leader of the IMF is initially Dan Briggs, played by Steven Hill . As an Orthodox Jew, Hill had to leave on Fridays at 4 p.m. to be home before sundown and was not available until after dark the next day . Although his contract allowed for filming interruptions due to religious observances, the clause proved difficult to work around due to the production schedule and as the season progressed, an increasing number of episodes featured little of Briggs . Hill had other problems as well . After cooperatively crawling through dirt tunnels and repeatedly climbing a rope ladder in the episode "Snowball in Hell," in the following episode ("Action!") he balked at climbing a stairway with railings and locked himself in his dressing room . Unable to come to terms with Hill, the producers re-shot the episode without him (another character, Cinnamon Carter, listened to the taped message, the selected operatives' photos were displayed in "limbo", and the team meeting was held in Rollin Hand's apartment), and reduced Briggs' presence in the five episodes left to be filmed to a minimum . As far as Hill's religious requirements were concerned, line producer Joseph Gantman simply had not understood what had been agreed to . He told author Patrick J. White, "' If someone understands your problems and says he understands them, you feel better about it . But if he doesn't care about your problems, then you begin to really resent him . Steven Hill may have felt exactly the same way ." </P> <P> Hill was replaced without explanation to the audience after the first season by Peter Graves playing the role of Jim Phelps, who remained the leader for the remainder of the original series and in the 1988--1990 revival . </P>

Who played ethan hunt in the original mission impossible tv series