An Australian daily accessed 22,400 leaked pages of classified data on India's Scorpene-class submarine.
It was midnight when the phone at the home of a senior Navy officer posted at the Delhi Headquarters rang. "The Australian has published a report claiming details of Project 75 have been leaked," the caller said.
Project 75 is the official name for the Scorpene submarine project. Minutes after the midnight phone call, the Chief of Navy Staff Admiral Sunil Lanba was informed.
Defence Minister Manohar Parrikar was simultaneously informed and he immediately asked the Navy for an assessment of damage and to find out where the leak could have happened.
On Wednesday morning Mr Parrikar told reporters, "We knew about this last night." What he did not detail was the hectic activity that followed through the night.
By about 1 am, all hands were on deck at the Navy's South Delhi office from where Project 75 is monitored.
Some officers painstakingly compared the original Scorpene documentation with the papers published by The Australian. Others were tasked with checking which officers had accessed the document and where the documents had moved to look for possible points of leakage.
A screenshot of one of the pages of the leaked dossier on India’s Scorpene-class submarine
Simultaneously, the Navy's cyber experts, considered some of the best in the country, were looking for traces of possible leaks from computers in India and the cyber trail of the documents put out by the newspaper.
In Mumbai, a similar exercise was under way at the Mazagon docks - the shipyard where the submarines are being built.
The multiple checks ran through the night. In the morning, bleary-eyed officers were allowed to go home for a quick shower and shave. Within the hour, they were back at their desks.
The initial investigation report, short and factual, was placed before the Defence Minister, who was in his office by 10 am after attending a function, despite being up till 4 in the morning.
The leak would be discussed in the afternoon at a meeting of the Cabinet Committee on Security or CCS, the highest decision making body on security affairs headed by the Prime Minister.
As Mr Parrikar left for the CCS, he asked the Navy to issue the first official communication, which said documents had not leaked from India. The experts who had worked through the night, told the ministry that the cyber trail of the leaked papers didn't originate from India.
Soon after Mr Parrikar returned from the CCS meeting, he was briefed again by the Navy Chief. It was a longer briefing, on the possible fallout of the leak.
The Navy's conclusion did not change from the initial assessment it had given to the Ministry.
Mr Parrikar was told that India had signed the deal with M/s Aramis and not DCNS. M/s Aramis was bought by DCNS subsequently. The leaked documents showed they were from DCNS. The minister was also told that the specifications in the leaked documents didn't match.
"The basic shape, structure (of the submarines) like its height etc remains the same, but several modifications are made to suit our requirements. To put it in simple terms, the computer programme Windows has some basic similarities but Windows of 2007 and 2010 differ hugely," a senior officer associated with the exercise told NDTV.
By late evening, Mr Parrikar and the Navy sat down again. The Navy reiterated that all checks pointed to an overseas leak and the damage, if any, was minimal.
The Minister asked the Navy to shoot a query to the French manufacturer DCNS to investigate the leak and come back to India.