Truth will out
One way or another, in spite of all efforts to conceal it, the truth will come to be known.
Idioms and Phrases with truth will out
The facts will be known, as in She thought she could get away with it, but truth will out, and I'm sure she'll get caught. Shakespeare used this idiom in The Merchant of Venice (2:2): “But in the end truth will out.” Also see murder will out.