The short answer is that your story will be kept confidential wherever possible. Employers must be incredibly mindful when an employee comes forward with such sensitive information. Any reports of harassment, violence, or sexual harassment should be dealt with carefully, not unlike any other confidential information, such as medical records, etc. Employers should be cautious that no one except for necessary individuals should be able to access the information, and it should be absolutely shielded from spreading throughout the workplace.
However, a crucial element of any investigation is giving the accused the opportunity to respond to the allegations made against them. This includes providing them with the necessary detail, ideally in advance of their meeting with investigators, so that they can refresh their memory and are able to provide their complete account of the incidents. That does not mean that an accused’s story will be believed – an investigator will make that decision after speaking with all relevant parties. However, this does mean that an accused will be informed of your allegations, even though they too will be advised to keep everything confidential.