The second version of the Scalp Cut described by Meyer occurs in the Nach or after. This is essentially a response to cut that is thrown outside measure.
The sequence it pretty simple. When you see the opponent about to throw a cut, you cede the body by bringing your front foot back to meet your rear foot. At the same time you raise your own sword high. As soon as his blade passes by your hilt, you spring forward with a cut to the head.
Timing is essential for this to work. If you retreat too quickly he will abort his attack, too slow and his cut will land. You must spring forward while his sword is still falling lest he have a chance to counter-attack.
That said, this is a beautiful move when you pull it off. Quite often the opponent won’t even realize they missed until they get bopped in the head.