I enjoyed it SPOILERS. But I found the mystery initially annoying because everything is built around sheer overreaction. I'm all for the unforeseen but why freak out because you've got a double.? Why freak out at all all the small things that happen? It's not like anyone knows any hidden information. This story only works if the confusing and idiotic elements of the story are either supernatural, dreams/imagination. I take it as dreams /imagination.
The mother mentions acting to the non acting double, which she wouldn't have known, so she is aware of something (or was it his imagination ). She also offers blueberries as to check who she is talking to. This now suggest some split personality present. The spider could be his fear of cheating in a hallucination form, which stemmed from the strip club. Or even entrapment into a sedate oife as he finally views the preganat woman as a spider. Maybe the actor character was dreamt up to impress the stripper and be a cover persona. Later on she is suprised to find a ring mark on his finger. This could be a re-living on an event or the actual double stealing the others life and being found out. This movie is very open to interpretaion, but I think the enemy is the man himself, he is his own worst enemy. I think the point of this movie is to be ambiguous and let the viewer decide what's right. I think think I'll ever watch it again though as it's more of a decipher movie rather than entertainment.