This is another play, the third one. He beats aside his enemies sword which he takes with his left hand, and strikes to the head. In the same way, you could strike with a thrust.
The thing that stands out most about this play is its similarity to the 2nd scholar of the 2nd master of sword in two hands. The set up is different, but the concept of controlling your opponents blade with this grab is identical, and is the heart of the play.
From the cover of the 8th master of horse, strike up over your horses head and across, beating your opponents sword aside. Follow the natural turn of your body. Reach out with your left hand, and grab your opponents blade with your thumb down. For your own safety, the horses will need to be reasonably still, relative to each other. The faster the horses move past each other, the harder it is to grab the blade in the first place, and the more likely it is to slide in your hand and cut you.
Turn your opponents sword across to your left. You are really aiming to just pivot the blade around your opponents wrist rather than pull it out of the way. Your sword will already be chambered in Posta Fenestra as an end point to the beat. Moving your opponents sword like this leaves you a clear line to cut or thrust to their head, as the picture shows.