The Sensex opened almost flat at 13,651, down one point. Fresh buying in the opening trades, in line with a recovery in global markets, saw the index rally to a high of 13,748.Selling emerged in the latter half of the day, and the index slipped into the negative zone. A heavy round of selling towards the end saw the Sensex tumble to a low of 13,493 - down 255 points from the day's high.The Sensex, however, recovered some of its lost ground before settling at 13,566, down 86 points. The index has now dropped 3.2% (449 points) from its all-time closing high recorded on January 3.