I just finished reading "A Scanner Darkly" by Philip K. Dick and for some reason I am a little confused to the actual ending. Warning Spoilers Below!
It is clear that Bob Arctor is completely fried at the end and the brain damage is very likely irreversible. He is sent to the farm run by New Path that is growing the blue-flowered plants that are used to derive Substance D as a zombie, living in body but dead in spirit. It is also clear that Mike from New Path and Donna, who we find out is a Federal Agent, are working together.
There are two possibilities, as I see it. One is:
Donna and Mike purposely let Arctor fall into ruin so that they could get somebody inside the New Path farm and that hopefully this would help Donna's investigation into finding a major supplier of Substance D. In this scenario they may have been banking on Arctor somehow recovering his mind and giving useful information to Donna or Mike.
The other scenario that might make sense to me is:
The Federal Government is actually supporting the New Path program, and Donna as a Federal Agent is tasked with keeping this secret from other law enforcement agencies. In this scenario she purposely destroyed Arctor because she knew he was a narc and was trying to use her to find out who her supplier was. She clearly felt love for him though, and was torn with guilt over it.
Or perhaps I misunderstood the ending entirely and I have it completely wrong?