Percy didn't know what to think. His legs hurt, he couldn't breathe, but yet he wouldn't really have it any other way. He has tried many, many times before to put himself in the shoes of the mortals around him, but it is like his highly active ADHD brain refuses to give him a solid picture of that kind of life. So, he continues to sprint and fight for his life like he does on any other day. It wasn't until he saw the dark alley to his left that he knew the fight was over. He could have killed the beast right there on the spot, but who knows what the mortals might see. A lot of times the mist does not always play in his favor. He might be accused of killing some random person's dog and he really didn't feel like dealing with that today. Facing the hellhound, which by the way was making him late for his date with Annabeth, he pulled out riptide already forming a plan in his head. Well, what he calls a plan, which is basically to attack. Annabeth doesn't call him a Seaweed Brain for nothing. The hellhound sits back on his haunches ready to jump reminding Percy of when a hellhound first decided to attack him within his own camp.
He lets it leap towards him and watches its failed attempt to injure him with its claw. Percy jumps back, fakes a hit to the right, spins and slices riptide through the left side of the hellhound as it bursts into gold dust and makes its trip down to Tartarus. Well that was unpleasant, Percy thinks as he wipes the dust off of him. Trying to remember his original reason for walking down the streets of New York at this time, he puts riptide safely back in his pocket. Walking out of the alley, he notices the time on the very helpful TV screen across the street in the Deli and sprints in the other direction. He didn't have time to notice the well-known blond haired super soldier at the end of the alley who witnessed everything.