Being Asked To Speak "confidentially" With Hr Regarding An "investigation" Of My Manager.

In the state of Colorado.

Received an e-mail from HR asking for a 30 minute confidential call to "ensure a fair and comprehensive understanding of a situation," regarding my manager. I have only been here a short while, so I've got limited understanding of internal situations/politics, but I have reason to believe this may be related to some potential litigation with some colleagues of mine who were recently laid off/fired.

I love and need this job, but this company is a bit of a gong show internally, I don't want to get in the wrong side of a situation I don't understand, and I'm nervous about covering my ass in general here. Any advice on how to handle this call (or other actions I should take to protect myself from potential retribution) would be much appreciated.