How do Shadowdancer’s Hide in Plain Sight, Hellcat Stealth, and enemies’ darkvision interact?

I recently had a game where there was some uncertainty, so I’m here to ask you how this interaction works.

I have a character, a Shadowdancer. This character has also got the Hellcat Stealth feat. The character sneaks in pure darkness, no light at all, on an enemy with Darkvision. There is no cover. Does the character stealth with Hide in Plain Sight, Hellcat Stealth, or the character cannot attempt to stealth? Or does the character stealth with Hide in Plain Sight but with a penalty similar to Hellcat Stealth?