Q: We have been informed indirectly that an employee has been harassed (possibly on several occasions) by a senior colleague.  How do we handle it? 
This is a serious matter which should be handled in close consultation with your company’s legal counsel or an experienced external lawyer. By way of general guidance. It is critical to collect as much evidence as possible before confronting the alleged assailant.  Make sure you notify the employee making the complaint that you are actively investigating the issue and be as supportive as possible. If the matter appears to be an isolated incident and open to subjective interpretation, then an informal “friendly” warning may be sufficient. But if it is a serious case of harassment, or one that proves to have been repeated then it will be necessary to gain CEO backing and call the colleague in for a disciplinary meeting in the presence of a Director of the company and your legal representative. Very serious infractions will necessarily have to involve the police, as the employee will involve them if the company does not. Do not suggest the harassed person takes time off, as this can potentially raise a claim against you on the grounds of discrimination or constructive dismissal.