Understanding 'Unsettling' in Context

In the quaint town of Eldridge, the residents took great pride in their annual spring fair. Every year, the main square would be adorned with colorful banners, and the aroma of freshly baked goods filled the air. Children laughed as they played games, while the local artisans showcased their crafts. One stall, owned by Mrs. Thompson, was particularly popular for her handcrafted jewelry. However, amidst the laughter and merriment, there was an undertone of anticipation as everyone awaited the announcement of the town's best flower arrangement, a coveted title that brought with it much prestige.

During the fair, Mrs. Thompson noticed that some of her delicate necklaces had gone missing. She felt an unsettling mixture of frustration and apprehension, realizing that someone might have taken them without her permission. With a heavy heart, she decided to notify the fair organizers. The word 'unsettling' in this context means: