Annie,
I thought that we were seeing a very exciting scene for a possible Dark Shadows spinoff show: "Quentin Collins - Martial Artist!"
That "diving" karate chop that Quentin used on the always erudite Inspector Hamilton is, I believe, called a "shuto" in Japanese.
Who knows, the Q-Man could have been the next Bruce Lee, the next Stephen Seagal (Quentin certainly has the good, thick head of hair for that look!), the next Chuck Norris or, possibly, even the next Ralph Macchio (I can see it now: "Quentin Collins, The Twenty-Something Karate Kid"!).
Sayonara,
Bob the Bartender, a lover, not a fighter.