SUMMARY:
Feluda met a person named Batra from Nepal who told him that there was someone identical to him. He suspected that he might get entangled in difficult situations due to his doppelgänger’s wrongdoings. So, he asked Feluda to investigate the matter. Feluda also saw a man identical to Batra and determined a difference—the fake Batra was a lefty.
When Feluda returned from Esplanade, a man named Aniket Some called him to make an appointment. But before he could meet Feluda, a call came from the police saying that Feluda’s number had been found in a dead body’s phonebook. The victim was none other than Aniket Some.
From the victim’s diary and some investigation, Feluda learned that Aniket Some and Batra were both from Nepal and suspected that some shady business was happening there. Feluda decided it was imperative to go to Kathmandu. After arriving in Kathmandu, Feluda learned that Some was investigating fake medicine because he believed his best friend Himadri had been killed by a fake tetanus injection given by Dr. Dibakar.
While sightseeing, Tapesh and Jatayu saw the fake Batra. They followed him and found the godown of the fake medicine. They were seen but managed to escape and told Feluda everything.
While they were enjoying themselves at a casino, a lady approached and told them that her superior wanted to meet them. They agreed to go. The lady escorted them to a room where a person was sitting on a sofa. Seeing this person, Topesh’s heart skipped a beat—he was petrified to see the conniving Maghanlal Meghraj. They also saw the fake Batra, whom Maganlal called his right-hand man, Jagdish. They realized that this fake drug business was being run by none other than Maganlal. Maganlal threatened them to stop their investigation, but after returning, Feluda's investigation intensified, leading to the abduction of Feluda and his team.
After the abduction, when Maganlal was boasting to Feluda, he revealed everything about his business, not knowing it was a trap. The police arrived and arrested Maganlal. Feluda had recorded the confession where M detailed his fake medicine business. It was submitted to the police as evidence.
Through the ink of a fountain pen, Feluda identified that there was no fake Batra, a.k.a. Jagdish; there was only Anantlal Batra. Dr. Dibakar was also abducted. He SURMISED Batra when he saw ink stain on Batra's finger. He deduced When lefties use a fountain pen, there is a peculiar angle in which the pen erodes, and ink stains their fingers. the same stain was in Batra's right hand when he was trying to write with right hand in front of Feluda.
Feluda revealed that Dr. Dibakar was part of Maganlal's gang. Apparently, he did not give a fake tetanus shot accidentally; he poisoned Himadri because he was investigating the fake medicine gang. Feluda suspected him through his sudden surge of wealth and the opulence in his lifestyle.