What to do if the police has wrongly arrested my father

Hi Sir, My dad worked in a cooperative society as secretary for a salary of mere 8k per month. The president of the company has cheated and now the society is closed.Now the case is also in the court. My dad has signed on all depositors certificate. He was just a salaried employee. But police has arrested him as accused with 406 and 420 case. The police(dysp) clearly knows that my dad has not taken money and he was just a salaried employee but still arrested him. My dad is 68 years and his health condition is not good. What would be the consequence of this case. Is signing on a depositors certificate a serious offence. Will my dad be punished or can it proved that he is not guilty. In one of the document the president has also given statement that he has only done evrything. Please guide us as my dad is innocent