What can be done in California about a divorce agreement that was based on false information?

My fiance was divorced four years ago and agreed to release right to any accounts held in his ex wifes name. We recently found she had a secret bank account - statements mailed elsewhere, money deposited while they were married. This was never disclosed in any legal paperwork and if he had known about it, he would have never given up his rights. What can be done now?What can be done in California about a divorce agreement that was based on false information?
If she got all monies that were in the accounts he sign off on or if they split it 50/50. If you can prove what your saying they might charge her with fraud. Contact the lawyer that help him get divorcedWhat can be done in California about a divorce agreement that was based on false information?
She perpetrated a fraud on the court during the financial discovery phase of the divorce action. He may be able to recover all the monies he surrendered, plus interest. Contact a good attorney there to find out your options.
Nothing what was done is done and she obviously did this knowing all of that

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