He was going through the letters when a troubling thought occurred.

With this troubling thought in mind, the party hurried along the trail.

Meanwhile, Rick was having some very troubling thoughts of his own.

A troubling thought had lodged itself in his mind and he could not make it go away.

She pushed this troubling thought from her mind and kept tending to him.

Suddenly she stopped as a troubling thought occurred to her.

The troubling thought occurred to him that this woman had the gift.

But soon I began to have a troubling thought.

In the gathering night they walked along, close to each other, sharing the same troubling thoughts.

Then a troubling thought came to him, and he frowned.