He could feel the weight of the two walls pressing down on him. The car was no longer a car but the fist of some hideous monster snatching at the insect that Alex had become. (2.40)
In the course of a few days, Alex is thrown from his regular life into the harrowing world of spies and soldiers. It's no wonder he feels like an "insect."
Alex opened the window and climbed out. It was better not to think about it at all. He would just do it. (3.45)
As the old and often misattributed cliché goes—bravery isn't the absence of fear, but the will to overcome it.
He was sitting next to Wolf. To his surprise, the man was completely quiet, unmoving. It was hard to tell in the half darkness, but the look on his face could almost have been fear. (6.25)
Although Wolf torments Alex over his youth, he's as scared as a baby when he's up in the sky. Call it karmic comeuppance.
He was tough and he was fast—completing a thirt0ile hike as if it were just a stroll in a park. But he had a weak spot. Somehow he'd allowed this parachute jump to get to him. (6.30)
This teaches Alex an important lesson. It doesn't matter how tough you are, how strong you are, or how confident you are—everyone has something that makes them tremble.
Alex had almost managed to persuade himself that this whole business was […] a game. But looking at the cold face [...], he felt something stirring inside him and he knew it was fear. (6.73)
Alex has managed to control his fear so far, but the sight of Yassen Gregorovich reminds him that he has plenty to be afraid of.
Not for the first time, Alex felt very small and very young. Whatever was going on here, he knew he was way out of his depth. (9.86)
Maybe Alex would be less afraid if he was a seasoned superspy, like his uncle Ian, but who knows? Maybe Ian was scared out of his brains the whole time, too.
It was Yassen Gregorovich. Alex stared at him with growing fear. This was the contract killer Mrs. Jones had told him about. (9.87)
Although Alex is terrified of Yassen, he refuses to back down. All he would have to do is call MI6 and they would pull him out, but that's not even an option.
Alex knew he was in danger the same way an animal does. There was no need to ask why or how. Danger was simply there. (10.18)
In essence, Alex has learned to trust his instincts rather than his fear. This choice pays off, time and time again.
He stood there, balancing on the heels of his feet, like a matador. […] Now he was staring straight into the eyes of the rider, saw the man's uneven teeth as he smiled. (10.28)
This represents Alex conquering his own fear, playing a game of chicken with a bloodthirsty henchman… and winning. Boo ya.
Trying to fight off the sense of claustrophobia, he pulled out the flashlight and flicked it on. (11.45)
On the other hand, some fears are so hardwired into our brains that they can't be escaped. Wolf is afraid of heights; Alex is afraid of enclosed spaces; Shmoop is afraid of the world running out of pie.