Hamlet

Except, how?

If you convince your uncle that someone knows of his poison scheme, he might become scared enough to attempt to eliminate the threat. The trouble is, you would be the first person he suspects. Claudius will probably have you killed before you can even act on the information. You'd need to wait for a chance to pin this on someone else, a scapegoat who would have to receive your uncle's murderous attention in your stead.

There may also be a less costly, less risky way. Something you can act on now. People always fear the incomprehensible, the unpredictable, the unreasonable... They cannot factor it into their plans, so it unnerves them. It's why people always tiptoe around lunatics, be they the lowliest beggars or the mightiest lords.

So, what say you bring a bit of madness to Elsinore?