LE53 Blood Dragon Knight
Destruction only.
Action: When this unit attacks, deal damage equal to its power to target unit in the defending zone.

AU41 Take Captive!
Action: Take control of target attacking unit until the end of the turn. Move it to the attacked zone, declared as a defender.

If "AU41 Take Captive!" is played "in response" to "LE53 Blood Dragon Knight"'s action, does Blood Dragon Knight's action still work?

Thanks for Reply…

I would say Knight's action still works, as once action trigger is met, it resolves in separation from it's source. He must be attacking prior to being targeted by Take Captive, so trigger is met and damage should be dealt, after that he becomes defender.

However, I am only 90% sure of this ruling, so better wait for someone more adept at rules interpretation to confirm.

You are correct, Paradoks.