This is a high bind that locks you up well. I will take your dagger and throw you on the ground. Also I say I can dislocate your arm, but if you take your right hand with your left, you could counter me and I must let you loose.
Against an overhead stab, slide to the left slightly, so as to move off the centerline, and defend against your opponents attack as the 4th master. You use a sword grip to jam the forearm with your right hand by the wrist and your left in the middle of the forearm.
As they draw their hand back, you need to move with this momentum. With your left hand, ensure the arm folds back. Maintaining contact with the wrist, roll your right hand across the back of your left, to wrap your fingers over the top of your opponents hand. You will need to push your elbow forward to reach. This is the moment shown.
Let go with your left hand, and with your right cut straight down their spine. Your opponent will collapse backwards on the spot they were standing.
The counter to this move is that the player grabs their right hand with their left, and pulls it back toward the centerline. While doing this, they should keep their right shoulder low, and drive the right elbow up and around in a tight arc aimed at your face.
The twist will return all mechanical advantage to them, and tip you off balance, breaking your grip. The elbow will be extremely distracting at a minimum, and you will need to protect yourself against it. The two movements combined will leave your opponent fully chambered and perfectly placed to deliver a roverso strike to any available target on your right side or centerline.
You will see other variations of this throw in the following plays.