As the United States prepared 12 months ago for the historic inauguration of Barack Obama as the nation's new president, top-level officials of the incoming team and of the departing administration of George Bush were jointly trying to deal with a potentially devastating terror threat, which, in the end, proved not to be real.
Alarms were sounded – though never made public – when anti-terrorism officials revealed that they had what they considered plausible information about a group of Somali extremists crossing the border from Canada and potentially detonating a series of explosions at the moment that Mr Obama was being sworn in.
According to a report to be carried in next Sunday's New York Times magazine, the threat was taken so seriously that Defence Secretary Robert Gates, the only person who was to be carried over from the Bush administration into the cabinet of President-elect Obama, was dispatched out of Washington and to a secret location where he remained until after the inauguration was over.
If the worst had happened and Mr Obama and Vice President-elect Joe Biden were not sworn in and killed, Mr Gates would be next in line to be president.
"All the data points suggested there was a real threat evolving quickly that had an overseas component," Juan Carlos Zarate, Mr Bush's deputy national security adviser for combating terrorism, is quoted as telling the Times writer. The signs of a plot "seemed to be growing in credibility and relevance."
While the public was oblivious to what was happening, the hours before the inauguration saw frenzied activity by anti-terror leaders and top aides to both Mr Bush and Mr Obama, the Times said. It included a meeting shortly before the swearing in of the country's top national security aides inside the Situation Room of the White House.
Condoleezza Rice and Stephen Hadley, who had worked on national security for Mr Bush, wrestled alongside Hillary Clinton and James Jones, now the national security adviser, over what the response would be in the event the bombs did go off and the swearing in ceremony dissolved into a potentially bloody shambles.