In 1992, the Harshad Mehta scam led to profound changes in capital market regulation and infrastructure. One of these was setting up the NSE as a cleaner alternative to the century-old, scam- and faction-ridden BSE. In a supreme irony, NSE itself got embroiled in the algo scam originating in the Exchange’s sanctum sanctorum: the co-location servers for high frequency trading. Were systems deliberately weak to allow unfair access to certain brokers? Did NSE employees collude with them? Who was responsible? Here is the whole story of NSE’s commercial success leading to arrogance and fall from grace, even as it continues to remain a highly profitable near-monopoly.