For some reason, this movie didn't work for me. The characters were good, and the acting and photography were enjoyable, but the plot was just a bit lame — especially the ending when it was discovered that the nurse who did the killings had it out for the postman for letting her mother die in an earlier raid, which I thought was a pretty unlikely motive. The green in the title refers to the color on the bottles used to administer anesthesia — the nurse painted the carbon dioxide bottle so it looked like oxygen.