The Man Who Wasn't There

 Mr. India is easily the most famous movie about an invisible hero, but it's far from the only one.  Elaan (1971) also features the hero given a high-tech invisibility ring by a friendly scientist, but while Mr.India is a superhero movie at heart, Elaan feels like a spy movie. Specifically an Italian Bond knockoff from the sixties.

Naresh (Vinod Mehra) isn't a superspy with an eye for the ladies, though. As the film opens,he's a freelance journalist with an eye for one particular lady: Mala (Rekha). They meet on the beach, and Malais offended at having her picture taken, so she rides off on a horse and in a huff. The horse promptly gallops out of control, giving Naresh a chance to ride to the rescue. That doesn't impress Mala, because she's unconscious, but it does impress her father, newspaper publisher Mehta (Brahm Bhardwaj), who offers him a job. After further humorous misunderstandings, Mala falls for Naresh as well, and they're soon a happy couple.

Mehta assigns Naresh and comic relief sidekick Shyam (Rajendra Nath) to investigate an apparently haunted island.  It turns out that the island is the base for an international syndicate of unspecified evil, and after a little torture to establish that Naresh and Shyam aren't police officers, the Boss (M. B. Shetty) sends Lily (Helen) to perform an item number and then recruit them into the organization. Shyam does have an eye for the ladies, so he distracts Lily and the other femmes fatale, while Naresh sneaks off and gets captured again.

 Naresh is thrown into a cell with violent criminal Ram Singh (Vinod Khanna) and an ailing scientist (Ratan Guarang).  Naresh is kind to the scientist, who gives him his hidden atomic ring, which can be used toi turn invisible when placed in the mouth, though only if the user is completely naked.  Ram Singh just gives Naresh punches. With the help of the ring, Naresh and Shyam flee the island.

The Boss sends Lily and Ram Singh to kill Naresh and retrieve the ring,  as well as to collaborate on a counterfeiting scheme with shady hotel owner Verma (Madan Puri doing his best Adopho Celi impression) and his hypnotist sidekick, the Professor (Jankidas.)  (Verma's gang is largely made up of beautiful women who may or may not have been hypnotized.)  

 Along the way, Mehta is murdered, and Naresh, Shyam and Mala all wind up under the protection of the Central Bureau of Investigation.  In the day or so since her father's death, Mala has become a trained and certified CBI agent ("People change," as she explains to Naresh) and she's sent undercover as "Mary" to infiltrate the counterfeiting scheme, while Naresh and Shyam are sort of deputized and given silly disguises and sent to verify that yes, that is Lily performing at Verma's nightclub.

In a proper Bond movie, or even a high end knockoff, the characters would be traveling the world at this point, bouncing from one beautiful city to the next; even Operation Kid Brother managed to include visits to Malaga, Morocco, and Munich.  Not here, though.  Mala hangs around Verma's place waiting to be shown the counterfeiting machine, Naresh alternates between acting as Mala's invisible guardian angel and bumming around Bombay in a series of silly disguises, and the Boss, Verma and Ram Singh all compete to see who can betray the others first.

This is Bond on the cheap, with an equally budget friendly sci-fi twist; the fact that the ring only works when the user is naked means that the producers don't have to spend any money on partial invisibility effects. It's all very slight and very silly, and nobody ever dresses up as Charlie Chaplin, but it's reasonably entertaining, there are multiple Helen dance numbers, and Young Rekha is adorable.