A meeting between an assassin named Paul Kaytes and Colonel Zaman, the chief military advisor to an Arab king who is visiting the United States, has gone awry as the assassin is not pleased with the conduct of his hirer. He sets off with the intention of not following the man's advice to shoot him with armor piercing bullets, instead opting for a head shot.
The meeting takes place in Niagara Falls, and Tod and Linc just happen to be in the area on a combination vacation and temporary job. As they arrive, Tod receives an itinerary for the king. He heads to his room trying to figure out what is going on, only to have a pitcher of martinis thrown in his face by a woman the assassin assaulted before his meeting. The colonel is alerted by Tod, who promises to follow up. He warns the assassin not to get near Tod, as he is Tod's doppelganger.
Meanwhile, Tod drops Linc off in downtown Niagara Falls, where he runs into Kaytes in a department store. Not knowing what is going on, he strikes up a conversation with the assassin only to leave put off by his brusque manner. Linc is forced to catch a bus back to the hotel where the two are staying and expresses his displeasure with the actions of Kaytes (believing, of course, that he is Tod).
Confused, Tod heads out later that evening where he runs into Kaytes. Having been briefed on who he is, the assassin introduces himself to a surprised Tod and informs him of his purpose for being there...the assassination of the king. Tod begins asking questions, trying to figure out what is motivating Kaytes. Kaytes confesses, after some prodding, that he is trying to make up for an unfulfilling childhood that he blames his father Virgil, an incompetent barber, for sticking him with.
Later that evening, the assassin discovers that the federal government has caught wind of his plot as he and Tod are trailed by an agent who Kaytes guns down. The king touches down the next morning in Niagara Falls and is informed that Colonel Zaman is behind the entire plot and is advised not to disembark but he refuses to believe it and leaves.
Meanwhile, Tod is being held aboard a houseboat where Kaytes informs Tod of the exact time he plans to execute the act and that Tod will be the next victim. He then leaves, but not before placing a call to Linc in the hotel. Linc, still upset over what happened the day before, is still unaware of what is going on but does as Kaytes asks and believes Tod never came home (which, in reality, he didn't, but not for the reason Linc believes), which is to cover him on their temporary job.
At the hotel, the king decides to test the colonel's loyalty to him and force him to take his place in every function, as people won't know the difference if he's wearing the king's headdress and robes. Zaman decides to go along, as the king will wear the colonel's uniform instead.
Kaytes decides to attempt to kill Tod, but he can't as he has second thoughts. Instead, he takes Tod back to the hotel and orders him to keep quiet. He, meanwhile, goes to the job with Linc and says that if Tod goes to the authorities he will kill Linc.
While the two men are working on equipment at the falls, Linc realizes that Kaytes, whom he still believes to be Tod, is acting strange. The king's entourage happens to pass by just as this is happening. Kaytes moves into position as Linc watches in shock, and he gets a clear shot and fires. The bullet strikes the colonel in the head, exposing the plot and neutralizing it as its originator is now dead.
Kaytes then takes off with Linc and the king's protectors in hot pursuit. He reaches the parking lot and intends to get away by stealing a car, with the Corvette free for the taking. Just as this happens, Tod arrives in a taxi which stops Kaytes in his tracks long enough for another assassin, who Zaman hired to take Kaytes out and cover his tracks, to take him down with a shot to the back. For his dying words, Kaytes says to Tod, "better me than you, huh kid?"