Arnold Gundars is one of the world's most successful illegal arms dealers. He manages to buy the Switchblade, the most sophisticated prototype stealth fighter plane able to become invisible to both radar and naked eye, from Lieutenant Percy and pays the BNS Special Agent Rachel Wright to help him. He later decides to sponsor the boxing match to be held in Budapest opposing the American Kelly Robinson and the European Cedric Mills in order to use the event to auction off the Switchblade.
On the eve of the match, Gundars organizes a reception at his palace during which he intends to sell the plane to one of the many criminals who are invited. There, he meets Kelly Robinson in person, however the latter is secretly working with the BNS and he manages to steal Gundars's pen and to replace it with a duplicate fitted with a tracking device. Shortly after, Gundars goes to his private office where he has a meeting with Zhu Tam, a terrorist that he invited, and convinces him to participate in the bidding, but unknown to them the BNS Agent Alex Scott is spying on them. After they leave the room, Scott tries to hack Gundars's computer, unfortunately Kelly Robinson enters and accidentally activates a silent alarm. Gundars returns to his office with another bidder a few moments later and one of his men informs him that the room alarm has been activated. They spot Scott and Robinson climbing on roofs and Gundars sends his men after them, but the two manage to escape.
The following day, Gundars decides to set a trap to eliminate the BNS agents. He sends several of his men to a bathhouse, then he goes there himself while Agent Wright, Agent Scott and Kelly Robinson are tracking him thanks to the pen tracking device. After spotting Scott and Robinson, Gundars's men attack them but they are all killed during the ensuing fight. Gundars flees in his car and Wright tries to pursue him, but her car explodes, although she only faked her death in order to fool Scott and Robinson. Meanwhile, some of Gundars's men go to the BNS base to kill all the other agents.
In the evening, Gundars has another meeting with Zhu Tam, who manages to gain the bidding. They then leave the palace to go on top of a tower of the Chain Bridge where the Switchblade is hidden and they conclude the sale. Gundars gives Zhu Tam the activation code of the plane that he obtained from Lieutenant Percy, but Alex Scott arrives and takes Gundars hostage to force his men to surrender. However, Rachel Wright suddenly attacks him in the back and disarms him, revealing him that she is a double agent. After Scott has been tied up, one of Zhu Tam's men enters the activation code of the Switchblade but it turns out to be a wrong code which activates the self-destruction of the plane. Gundars blames Wright for not having the right code so she decides to torture Scott in order to get it, but Kelly Robinson finally arrives while Scott manages to free himself and to grab a weapon, and the two set off a firefight. Another BNS Agent called Carlos arrives by parachute and kills several men of Gundars and Zhu Tam before taking the former hostage to force the others to surrender. Scott then gets on the plane to stop its self-destruction, however Robinson believes Carlos is also a double agent and knocks him out. Wright seizes one of his guns and shoots both Zhu Tam and Gundars in order to steal the latter’s briefcase.