That was something Alex liked about the outside. People were allowed to change their minds whenever they wanted. But it was a double-edged sword since people could change their minds in ways you didn't like without warning.
Someday Claire might change her mind about wanting him around. The very thought terrified him.
She was his lighthouse in a storm. The anchor that kept him from drifting away. The sun that lit his days and the moon that kept his nights from being completely dark. He had absolutely no idea what he would do without her warmth and love.
If Alex had been sent to kill anyone else that fateful day, he would still be the Agency's slave without ever being any the wiser. Sure, he had been bored out of his mind, but it was Claire specifically that intrigued him. No one else could have affected him enough to make him want more out of life.