Miss 420 is a story of a young recruit, who is assigned the all important task of trapping the people who are smuggling crucial defence secrets to interested organisations abroad. This spy, Miss 420 (Sheeba), is approved by the second in command in the Intelligence Department, Mr. Khan (Tinnu Anand). The Chief of the Department is Col. Kapoor (Shakti Kapoor). Miss 420 is escorting a van carrying the secretes, when the villians DK (Mohan Joshi) and his gang attack the convoy. The secrets are not found, but Miss 420 is dead!
A similar looking girl is spotted on the shores of Mumbai with Vicky and Varun, two young fun loving college students (Baba Sehgal and Jeet Upendra). Vicky finally manages to convince Anamika (Sheeba) about his love for her. Anamika's brother Anand (Aasif Sheikh) is a crime reporter working for Goa Times. He follows DK from an official function, up to his house and finds startling facts about this fraud, who puts up a front of being an honest businessman, but as luck would have it. Arvind is spotted with his camera and after a long chase, he leaps to his death from a mill.
Anamika arrives in Goa and is shocked to find that her brother has not come to receive her. Vicky who had driven their well in advance to receive her offers his help but Arvind is no where to be found! The plot thickens when Johny and Waqar, two detectives (Mushtak Khan and Arun Bakshi), report spotting Miss 420. Khan is shocked as Miss 420 was presumed dead. Now starts the cross fire. The villains desperately need the film roll that Arvind has clicked, and that was never found. Arvind is alive, but has lost his memory!
How will the villians organisation and the traitor in the Intelligence Department. be caught? Will Vicky get trapped in this cross fire? Is Arvind faking his condition? Who is the missing link in the Intell. Dept.? Who is the real Miss 420?