need help for my sis-in-law, working illegaly in china

her contract has expired last aug., 7, 2015. her employer brought her to PRC, but did not renew the contract, for the promise that they will pay the penalty, and wanting her to work for 3 more years. she directly trust thier conversation. now that she finally decided to go home, employer does not allow her to go home. worst is, employer keep her passport. and telling her again that she can only go home in the year 2020 and they will pay the penalty. please help me so my sis in law can go home safe. she really want to go home asap. what should we do? we need your help. can Chinese police fetch her so she could bring her things too?