In 1790, a ship was sunk by a typhoon in the South Seas. A man, his wife and their small boy survived the disaster. They drifted to a small tropical island and found only rare life-giving herbs for food. The man and his wife died but the herbs preserved the life of the boy. One-hundred fifty years later *, a ship stopped at this unknown island and an old man was taken away from its shores, setting up a home base in London the old man, who was that lost boy, found that without the herbs, he would soon die.
Known as Mr. Elixir to his neighbors, he feverishly attempted and succeeded in creating an elixir that when pored over normal herbs had the same effect as the ones on the island as well as letting him keep his super-strength.
The old man then befriended a neighbor to help him fight organized crime. Having studied hypnosis and stage magic (though having lived most of his life on that island it’s never quite explained when he did this studying), he also would catch crooks by setting them up, then tipping the police via radio message as "Elixir—The Voice."
As an "invisible detective," (he couldn’t turn invisible; it was just that he didn’t let anyone see him) The Voice then began fielding requests for help and installed a special one-way mirror. He would speak to potential "clients" from behind it, and then set out on the case, using the fact that no one expected a man of his age to have such fantastic strength to his advantage.
* Shades of Tom Strong!