Old TV Western memories needed

Old Western (TV?) where killer is a young man pretending to be a young woman. There is a group out on the trail and people are being killed one by one until the killer is unmasked. I was thinking it was a Maverick or Cheyenne episode but Google and AI are no help. I know it's a rather unusual topic for that time, but I'm pretty sure I remember it. Any help will be appreciated. Thanks.