In every case of a
concealed fraud, the right of any person to bring a suit in equity to recover
any land or rent of which he, or any person through whom he claims, may have
been deprived by such fraud, shall be deemed to have first accrued at and not
before the time at which such fraud is, or with reasonable diligence might
have been, first known or discovered: Provided that nothing in this section
contained shall enable any owner of lands or rents to have a suit in equity
for the recovery of such lands or rents, or for setting aside any conveyance
of such lands or rents, on account of fraud, against any bona fide purchaser
for valuable consideration who has not assisted in the commission of such
fraud, and who at the time when he made the purchase did not know and had no
reason to believe that any such fraud had been committed.