SPOILERS LURK BELOW…
Jake Gyllenhaal has a problem. Himself. After spotting his identical self as an extra in a movie, Professor Adam becomes addicted to finding the imposter. From stalking to shady (literally) phone calls to eventual face-to-face interactions with a woman named Helen, Professor Adam cannot for the life of him understand why this look-alike exists. And it is boldy shown how much cooler our imposter, Cool Tony, is than Professor Adam.
Professor Adam has the same routine. Every day. Like clockwork. It's simplisitc, mundane and uninvolving. His relationship with women is minimal and the relationships he does have – his girlfriend and mother – are, again, boring. But why does Adam bore us so much? He is obviously a smart man so why is his life such a drag. After scene after scene of this routine, we understand this life has been consiously chosen. Adam is not "lost" or "confused about life." He has made an effort to obtain this lifestyle. But…why?
Although his delivery is disengaging, Professor Adam's knowledge on totalitarianism is vast. He can link each thread until an entire, coherent web is produced. He understands what history showed us with individuals over-stepping his or her boundaries and engulfing a society, or potentially just one other person. As Adam paces around his classroom with confidence, he finds in front of him a lecture hall populated with yawns and scribblings in-between the margins. The one place he can flex power proves to be a dud of an engaging environment, even for him. We get our first glimpse into the "suppression" Professor Adam has endured.
As our plot moves onward, we see more and more of Anthony. He's cool, cocky and can ride a motorcycle. The two finally come face-to-face with each other, but Professor Adam nervously exits and becomes freaked out. Alongside this dim-lit hotel meeting, we are plagued by visions of spiders. Women as spiders, giant city spiders and spiders that Anthony seems to like seen crushed in shady sex shows (refer to opening scene). Finally, we see the one image our entire story has lead to, a giant, scared spider. As Professor Adam gets more and more involved in Cool Anthony's life, he overtakes it. Girlfriends are swamped and the two seamlessly switch lives. But…huh?
The Zinger, if You Will: Professor Adam and Anthony are one in the same. They are the same person. Professor Adam has been suppressing Cool Anthony (his old, womanizing self) and has now gotten back into that lifestyle.
But What About All These Damn Spiders? Nope, no alien/sci-fi ties here. This is a metaphor. Spiders are how Anthony views women. He feels as though they entrap him and try to keep him tied down in a web of dramatics, loyalty and family (ie. the baby on the way). Cool Anthony is just that…too cool. He does not want to settle down and be a family man. No sir. He wants sex shows and misogyny.
That Final Scene: This is simply Professor Adam's final transformation back into Cool Anthony. He sees the key to his exclusive sex show club and this is the final catalyst that fully brings back Cool Anthony. When Cool Anthony witnesses Helen turn into a giant (and scared) spider, we see our final image – his smirk. He is back to misogyny and wants to stomp on spiders (aka women) again so he is not "ruled" and "entangled" by women.