Their trek is uneventful, for a value of 'uneventful' that includes occasionally fighting monsters. The chocobos make them reach the end of the Highroad much earlier than they otherwise would, and there they see Dona arguing with a Crusader, Barthello in tow.

That way he goes!

Can he discern anything about why she's arguing with one, or does she notice him and stop?

She does not immediately notice the party.

"How many times do I have to tell you?" she asks the Crusader. "I'm a summoner!"

"Sorry, ma'am!" he says. "No exceptions!"

"You dare impede a summoner's pilgrimage?"

"Sorry, ma'am! No exceptions!" he repeats.

"Useless!"

Well that's curious! He'll land and interrupt her since, y'know, that sounds like fun.

"Hey."

She turns around. "Oh, it's you. As you can see, not even summoners can pass. But they'll call on us in the end. Just wait and see."

"I have no idea what we're not allowed to pass, here!" responds Theo, smiling slightly.

She points at the Highroad Northern Gate, where a caravan seems to be stopped, blocking the way.

"… Okay and why are you not allowed to pass it, any idea?"

"Apparently no one is allowed through until this 'Operation Mi'ihen' is done with," she says with some scorn.

"...why?"

"You could try your luck at getting an actual explanation out of him."

So Theo turns to the guy! "… What's the issue with us going through? I mean, I have wings so I could just fly over, should I also not do that?"

The guy looks at him. "We would strongly recommend you not to do that while the Operation is under progress, sir!"

"– Would it be dangerous for me, or is there something you don't want me to see, or…?"

"It would be very dangerous!"

"I'm invulnerable, so probably not dangerous for me…"

The Crusader stops. "Please do not interfere with the Operation, then."

"Would I be interfering by going and looking or do you mean, don't go interrupt them?"

"Don't interrupt them," he agrees.

Theo looks like he's about to go, then– "Estimate for how long they'll be blocking the way for?"

"The Operation will take place tonight."

"… And be cleaned up by the morning or–?"

"We will celebrate Sin's destruction in the morning!"

Theo pauses. "Okay so I'm just gonna ask you a few more questions about this before leaving, I think. Why are you so confident it'll be destroyed and can I know what you're using?"

"We're bringing Sinspawn from all over Spira here to lure it into a trap! This operation is a joint effort between Crusaders and Al Bhed. We'll lure Sin in, and the Al Bhed will strike it down with powerful ancient machina!"