"I have no idea. Maybe it was the statues."

"Of course it was the statues. I'm trying to figure out who helped them. Who sided with the statues against their own people."

"I wish you the best of luck."

"Couple things from my room I'd like back."

"I'll let her know. What things?"

He lists them.

"Okay, I'll let her know. She doesn't want to actually hurt you."

"She hasn't. I just wanna know who's her inside agent."

"It's not me and I don't know who it is."

"Okay."

"I understand why you would think so, but honestly I'm not yet sure enough this won't end in tears to be willing to get involved. Good skill finding the culprit."

"Thanks." And he goes off to corner his brothers.

And Marille goes off to tell her sister to give his stuff back.

NIce of her! He believes her about not being involved but he can't figure out who was.

Excellent.

The next day every item on the list he gave Marille is back in his room with a brightly-colored ribbon attached to each one.

He considers various methods of laying a trap for the intruder and settles for moving out of the house without telling anyone where he's going. 

And finding her glitter source and covering her whole floor in several inches of it.

She sweeps up the glitter carefully and considers her next move. Without as easy access to his environs she's at a marked disadvantage.

She acquires materials and tries to find him.

That's going to take some doing. He rode with Oromë for nearly a hundred Years.

He has to resurface some time. Presumably. She can wait.

Oh, sure, he'll stroll into the city every few days and pick up miscellaneous things and play with his kid brothers. But then he'll leave, and she can't follow him.

Can she enlist the aid of his kid brothers and/or her secret insider to lead him into a trap on one of these incursions?

Probably. What's the plan?

Overpowering floral scent. And glitter. And bright pigments.

"Sure. This is ridiculous, though."

"That's why I can't get Marille to help."