amazing film for certain. ive only seen it twice. but for some reason cant really understand it.

to my perspective:

donny gets these weird trips for what he thinks are from his pills. they make him do dirty deeds (done dirt cheap). and pretty much fuck shit up for everyone around him. he finds out about time travel and then somehow reverses time to where he dies from the plane motor crashing through his house...

can anyone fill in the blanks for me?