A party that breaks the trust of their closest contact irrevocably blowing up a relationship will not find it difficult to repeat this with others. Whether you are a customer, investor, or employee, when the value of deceiving you exceeds the value the party perceives in you, they will not hesitate to seize the opportunity.
Giving them a second chance is mistake I have made and one that I witness far too often.
Sometimes the best thing to do is to just move on. The value of your most powerful contact is null or negative if you are unable to trust them.