Ashok Roy is a rich and renowned youth with a lovable personality. He mingles freely with the people and is extremely popular.
Having been denied the love of parents, Ashok nurses a special affection for orphans and runs and orphanage, Parvati Mandir, with the assistance of his friend Mahesh.
Seema is the niece of the Inspector General of Police. Her first encounter with the Ashok leads her to think that he is an ordinary person and she ignores him. However, when she meets him again, she has to revise her opinion. She had gone to him to sell tickets for a show in aid of Defence but Ashok surprises her by signing a cheque for Rs. 3 lakhs in furtherance of a worthy cause.
Seema now meets Ashok quite often. She also gets acquainted with the activities of Parvati Mandir and is increasingly drawn to Ashok. But their intimacy the invokes wrath of Ramesh, who though betrothed to Seema, has fallen from her grace owing to his uncouth and unseemly activities. Unable to witness the romance, between the two and burning with jealousy, Ramesh seeks the help of Ajit, who is a traitor and tho leader of a gang of smugglers. Ramesh is a mere puppet in the hands of Ajit, we know the explosive secret surrounding the life of Ramesh......that he is a fake grandson of Rai Bahadur Jwala Prasad.
Ramesh and his henchmen attack Ashok when he is engrossed in watching Seema's dance at the Defence show, of which he has been made the chief guest. A gun explodes and the hell plunges into darkness. In the ensuring confusion the crooks manage to decamp with Seema. However their plan to eliminate Ashok has miscarried, the bullet having missed its mark and instead next to Ashok.
When Ashok learns of Seema's fate he disguises himself and pursues the crooks and eventually rescues his beloved. The incident brings the two still closer and they decide to become man and wife.
Professor Choudhury goes to Parvati Mandir to thank Ashok for his valorous deed but when he encounters the statue of Parvati, his heart misses a beat. The statue of his wife and he suddenly realises that Ashok is none other than his long-lost son and the real grandson of Rai Bahadur Jwala Prasad.
But before he is able proclaim this secret to the world, yet another mystery hits him like a tornado and seals his lips.
This new secret concerns Ashok, his son, who, in addition to being a rich and respectable citizen, is the notorious night robber "Jugnu" (glowworm), on the wanted list of the Police for several years.
Why Ashok disguises himself as "Jugnu" and what compels him to lead a double life is a million dollar mystery which will be revealed to you in our film "JUGNU".
(From the official press booklet)