The Sensex opened with a negative gap of 350 points at 18,012, and soon slipped deeper into red on global cues. Unabated selling in the morning session saw the index slip to a low of 17,443 - down 919 points from the previous close.Buying at lower levels saw the index recover smartly, and touch a high of 18,213 - a recovery of 770 points from the day's low.The Sensex eventually ended (provisional) with a loss of 231 points at 18,131.