The Workplace Investigation Guide

Guide me on handling this workplace complaint/investigation properly.

The situation: [DESCRIBE THE NATURE OF THE COMPLAINT AT A HIGH LEVEL]
My role: [MANAGER / HR / OWNER]

Provide:
1. The immediate steps (take it seriously, preserve confidentiality,
   consider interim measures)
2. A fair, consistent investigation process at a high level
3. How to interview parties fairly and document properly
4. The principles: impartiality, confidentiality, no retaliation, due
   process
5. Where I absolutely must involve professionals

Be explicit that this is orientation only — investigations touching
harassment, discrimination, or serious conduct must be run with qualified
HR and legal support, and I should engage them now. Flag the legal
exposure of getting this wrong.