Mary Soto, the controller of My Citizens Company

Mary Soto, the controller of My Citizens Company, has gone over its inventory records many times and is concerned that one or more company employees has stolen large amounts of the company's inventory. However, she is not absolutely sure that any theft has actually taken place because large portions of the written and computer records are missing for unknown reasons. Still, rough calculations, based on total purchases and sales, show that perhaps 20% of the inventory is missing. Mary spoke to her internal auditors and demanded that they give her an explanation, but they said no explanation was possible without the missing records.

What should Mary Soto do? Should she contact the police? Should she hire an external forensic accountant? How might a forensic accountant help in this case? Specifically, what forensic accountants can do that internal auditors cannot do?