Darkness
Darkness has become the defining metaphor of the modern age. "They locked eyes and there was something there, a passing darkness, then it was gone, like a storm cloud drifting away." This example is typical of the utilization of metaphorical darkness. The comparison within the simile to a storm cloud is equally ambiguous yet immediately understandable. Darkness in the present-day vernacular is almost synonym with a nebulous evil that is unclearly defined yet unmistakable. In this instance, the darknes that Eric sees is set within the context of his not being sure whether or not Griffin is really joking or not about torturing his own pet gerbil.
Trust
Griffin is not the best person to get advice from and Eric begins to sense this early on with Griffin's definition of trust. "It’s like holding a winning lottery ticket. You just have to wait for the right time before cashing it in." Much of the story is actually about how much Eric wants to trust that Griffin's outward persona is the real thing and not just a false persona. The comparison within this simile is made as Griffin tries to justify stealing gum rather than accepting a tip from a grocery customer whom he helps with carrying bags to the car.
Griffin's Facade
Griffin does present an almost Jekyll/Hyde personality. "His smile was like a pure beam of distilled sunlight. His long lashes blinked, and his cheeks pinkened. He wore a perfect mask of kindness and light." Griffin is egregiously nice in public while showing a penchant for sociopathic behavior away from interfering eyes. The smile is deceptively brilliant and the description of it being like a mask is absolutely appropriate.
Doing the Right Thing
Eric is aware of the two sides of Griffin and really wants to do the right thing "A pressure was building, like air in an overinflated tire." This pressure is caused not just by Eric's understanding that Griffin is not what he seems, but that his dark side is a real threat. Eric himself is feeling like a target and it is no long just Griffin's bully pals. The entire student body has become aware of what is going on and the pressure is being inflated by those expectations as well.
The Threat
Eric's very first encounter with Griffin is a demonstration of the bully's ability to disarm before the attack. "Threat hung in the air, though no one had said or done anything wrong." Griffin arrives on a bike with several other friends shortly after Eric first David Hallenback running while splashed with ketchup. Griffin presents no overt menace and Eric will not actually see any overt menace from him for some time. Right from the first moments, however, he is already intuitively aware of Griffin's dual personality.
