Dick had to admit that Harley seemed to have handled to final member of the Joker's goons pretty well. A bit sloppy, perhaps, but then she'd received training to be a psychiatrist and gymnast, not a fighter. He'd probably need some serious medical attention pretty soon, no one likes getting beaten with a bat but Dick could afford to wait a few moments before calling the emergency services. Harley was potentially a much more useful lead to the clown than a few of his goon's.
Stooping for a moment to reclaim his billy club, he heard Harley protest her innocence of purpose and right to roam.
“Besides, it ain't none of your business what I'm doin.. Never really was for that matta!”
He span the club around in his hand and then snapped it back into its harness on his back with its twin. He thought he saw her almost flinch at the sudden motion and deliberately moved more gradually to straighten up and face her properly.
"You know, I seem to remember this outstanding warrant for you arrest... along with a waiting cell at Arkham. Ring any bells?" he said carefully, not exactly challenging her but not giving ground either. She seemed to ignore that, however, focussing on something else.
"Whatca doing stalking around me? I'M SUPPOSE TO BE A SECRET!” she growled, seeming almost offended that he even knew she was here. Nightwing supposed that it might seem a little suspicious, him turning up the moment she started something but a citizen of Gotham had to quickly get used to coincidence, it was a hazard of living in the city.
"Believe it or not Harley, we sometimes go after criminals who aren't you or your boyfriend. This time, I was watching these muppets. So I have you to thank for ending my time on stakeout, I suppose." he gestured at the unconscious or quietly moaning henchmen.
As he talked, he saw her attention wander. What was she thinking about? Come to think about it, why was she here, harassing random thugs often in the Joker's employ rather than with the man himself? The word around town was that her and the clown had recently had some sort of falling out and those fallings out usually ended with him doing serious physical damage to her. Maybe the straw had finally broken the camel's back and she was finally ready to start giving back some of what the Joker had been dishing out for years? One could but hope.
A lot of Dick's hope was dashed when he saw her sneak a glance at the gun on the floor between them. Dammit he thought as she feigned disinterest in both him and the weapon, turning away. With her back turned, he readied his wrist grapnel with an easy motion. When she spun around and started blabbing, it was pretty clear she was trying to distract him to make a grab for the weapon. She finally made her move with characteristic subtlety and restraint; she screamed “HEADS UP NIGHT-BRAIN! He he!” and tossed a chair in his general direction.
As it flew past his shoulder, Dick aimed the grapnel at the gun and fired. The pincer on the end of the gas propelled rope grabbed ahold of the weapon and, with the a flick of his wrist, retracted and sent it shooting across the floor towards him. He brought it to a stop by stamping down with one foot, not breaking eye contact with Harley. His stamp knocked the magazine out and crushed the trigger guard, just as he meant to. With a reload and a few moments work to bend the guard back into shape, it would be fireable but not before then. In a swift motion, he stepped sideways, retrieved the chair and set it back upright.
"I think that's a great idea Harley, glad you suggested it." He pushed the chair towards her across the floor and pointed at it, indicating she should sit. "Let's talk. How's the clown doing these days? Healthy? In good humour? Because I really need to find him and if he is all those things, to change that." Dick didn't want to bring up the Batman yet, Harley would likely do it for him if she knew anything and if she didn't, he saw no reason to inform her that he was missing.