A plan was forming in his head, and she wasn't part of it.

As she looked back at Ben, one word formed clear in her head.

That's when an idea started to form in his head.

That was when the thought she had been avoiding slowly formed in her head.

Even while the words were forming in his head he realized he'd held onto them too long.

She didn't dare tell him the idea that was forming in her head.

A germ of an idea began to form in my head.

The plan of the crime formed itself in your head.

Out of necessity, a new plan formed quickly in her head.

But what formed in his head now wasn't fantasy, it was a plan.