Question about Swan Lake choreography

I love Swan Lake, and my favorite part of all is the Pas de Quatre. But there is a part of this dance I don’t understand.

They start out at stage left (our right) and dance across to stage right (our left) and back. They do this twice. Then the music changes and they do a step that involves lifting one foot up to their opposite knee; followed by four iterations of what looks like going rapidly from third position to point. Immediately after that, they do something that I cannot figure out. I have a half-dozen different clips of this dance, and I have even watched it slowed way down because it goes by very quickly. But I still cannot tell what exactly they’re doing with their feet.

Does anyone know?