be onto something

be on to (something)

To discover, realize, or be in the process of doing something of great importance, value, or insight. Great work on this essay, Lindsay. I really think you're on to something here. Scientists now believe they may be on to a cure for cancer.
See also: on

be ˈonto something

know about something or be in a situation that could lead to a good result for you: Researchers believe that they are onto something big.She’s onto a good thing with that new job.
See also: something