Emily was really regretting what she did. She wasn't expecting that kind of effect on Oliver. The moment everyone else seem to be hallucinating about the ghost girl Alice, Emily noticed that something was wrong with Oliver.
Oliver was having a different reaction than everyone, he didn't look like someone was talking to him. Also his eyes were open, but they were unfocused. He was also sweating a great amount.
Emily couldn't understand what was happening to Oliver. So she took one of the gas mask she hidden in the bag she brought and put it on Oliver. The effects of the hallucinogen, from the candle she switched should be wearing off after a few seconds, since it wasn't that strong to begin with.
