As a boy, Bitzer is Gradgrind's best student. As a young man, he becomes the light porter at Bounderby's bank, spies on Tom and the other clerks, and only follows the economic principle of complete self-interest. At the end, he catches Tom trying to flee abroad and tries to bring him back to for the reward before being outwitted by the circus performers.
The three parts, or volumes, of the novel are named "Sowing," "Reaping," and "Garnering." These words make us think of farming, and also of the phrase "you reap what you sow" (which means, whatever you put out there, that's pretty much what you'll get back). Bitzer is basically a walking, talking example of just how that phrase works. He was Gradgrind's best student, and grew up into a man who puts aside every emotion and every kind of non-selfish motivation. Slowly and surely, he paves the way for himself to rise at the bank, until the last moments of the novel when he finds and arrests the escaping Tom, Gradgrind's son. Bitzer hopes that if he turns Tom in, Bounderby will give him Tom's old job.
What makes Bitzer extra creepy is how totally calm he is through all of this. It would be one thing if he were really angry with Tom, or jealous of his life, or some other normal human emotion. But no, he's just all business, a kind of economic Terminator – unstoppable, unbribe-able, unable to be begged for mercy. It's starting to sound a bit like a broken record here, but yes, Bitzer too works as an example of this kind of educational thinking run completely berserk. What happens if you don't teach kids to care? Well, what you'll get is some really cold adults.