Believe it or not, hired gunman John Baron (Frank Sinatra of "From Here to Eternity") wants to assassinate the President of the United States in this tense little suspense yarn so he can earn a half-million dollars. Baron claims that he has nothing against the president. Ole blue eyes and his two henchmen show up in the sleepy town of Suddenly, California, posing as FBI agents. Meanwhile, Sheriff Tod Shaw (Sterling Hayden) receives a telegram about the President's impending trip along with a request to provide transportation for the chief executive to a ranch. Secret Service agents swarm into Suddenly, and the Chief Secret Service agent, Dan Carney (Willis Bouchey of "Dirty Dingus Magee"), sends his men out to check all the buildings opposite the train station. Carney is particularly worried about a house at a hill that looks down at the train station. Shaw informs him that no assassin could hole up in that house. Shaw explains that Pop Benson (James Gleason of "The Clock"), a retired Secret Service agent with a bad ticker, lives in that house. Carney is surprised and pleased by this coincidence because he knows Pop. Nevertheless, he warns Shaw that a threat has been made against the President. Shaw and Carney climb into Shaw's black police cruiser and go up to Pop's house, never suspecting what lies ahead of them. While Carney has been squaring Shaw about the situation, Baron fools Pop, Benson's daughter-in-law Helen (Nancy Gates of "Comanche Station") and her son Pidge (Kim Charney of "The Werewolf")into believing that he is a genuine FBI agent so that when Shaw and Carney enter the house, everything appears calm and peaceful. When Pop mentions Baron's name, Carney tries to whip out his pistol, but he is shot to death in a brief gunfight that leaves Shaw wounded. Baron and his hostages begin the process of sweating it out in a house atop a hill near the railroad station until the chief executive arrives by train to go on his annual fishing trip. Helen's husband Peter is dead; he died in the war, so Helen is opposed to guns on any condition. She refuses to let Pidge watch either war movies or own a gun. Eventually, we learn that John Baron was a World War II hero who killed 27 German soldiers and received a Silver Star. He grew up as an orphan and drifted around America until he found a temporary home in the U.S. Army. Director Lewis Allen and scenarist Richard Sale maintain enough tension as our heroic hostages plot to thwart Baron. He has bolted a rifle to a table and positioned the table in front of the living room window with a clear view of the train depot. Things really heat up in the last quarter-hour after the television set repairman shows up. Sinatra is thoroughly repulsive as the psycho killer who was drummed out of the military on a Section 8. Reportedly, Sinatra pulled this picture out of circulation after the assassination of President Kennedy. Clocking in at a lean, mean 75 minutes, "Suddenly" lives up its name. The ending is ironic.