|Appearances||The Great Game|
Carl Powers was a school boy who died after what was thought to be a freak accident whilst on a school trip to a London swimming pool. At the time a young Sherlock thought the death was suspicious and tried to get the police involved but no one would listen.
Sherlock reveals that Carl Power's was the case that got him started, he explains the case to John while they are travelling in a cab during 'The Great Game'. This shows that Sherlock and Moriarty's rivalry actually started way back but neither party was aware of the other's involvement in the case.