Murder will out.

The next sentence of "paper can't wrap fire" can be "needles can't be hidden in cotton"

"Paper can't wrap fire" means that fire will burn paper, which means that the truth will always be exposed and can't be hidden. "A needle can't be hidden in cotton" means that even if the needle is hidden in cotton, it will be found, which means that the truth can't be hidden. These two sentences express the same truth: the truth will always appear, and lies and fallacies can't cover it up.