On the afternoon of Dec. 8, 1972, a Boeing 737 crashed into a residential neighborhood in Chicago, a mile and a half from Midway International Airport, where the flight - United Airlines Flight 553 - was headed for a layover between Washington National Airport and Omaha. Forty-three of the 61 people onboard were killed, as were two residents of a house where the plane came to rest.
Almost immediately, FBI agents descended on the scene, according to reports at the time.
The crash, a tragedy in its own right, quickly became something more: a source of conspiracy theories and a catalyst that helped bring the Watergate scandal to its conclusion.
George Collins, a congressman and a founder of the Congressional Black Caucus, was one of the passengers killed. So was Michele Clark, a young television correspondent for CBS News.
But public attention focused on another passenger, Dorothy Hunt. Once her badly burned corpse was identified using jewelry recovered on her body, reporters, already frenzied by Watergate, went into overdrive.
Dorothy Hunt was the spouse of one of the Watergate ringleaders, former CIA operative E. Howard Hunt. Hunt was under indictment in Washington, D.C., facing a trial with his co-defendants that was scheduled to begin the second week of January 1973.
Dorothy was later identified as the "paymistress" of hush money to the Watergate defendants and their families to keep the burglars from cooperating with authorities and testifying at the trial.
Investigators combed through the wreckage and found a packet of $100 bills totaling $10,000 in a purse belonging to Dorothy Hunt. It was also discovered that she had taken out a $225,000 flight insurance policy at Washington National Airport before departing.
Immediately, questions were asked: Was Hunt murdered to keep her from revealing that the White House was in on the coverup? Was a message being sent to all the Watergate defendants?
There is no question that Dorothy and Howard Hunt had been expressing extreme frustration with the lack of responsiveness by President Richard M. Nixon's inner circle and the erratic hush money payments that Howard complained were coming in "minor dribs and drabs." After Nixon's landslide victory in November 1972, Howard called his contact in the White House, Charles Colson, to warn that money was becoming a problem.
"The stakes are very, very high," Howard told Colson in a call Colson recorded on his Dictabelt, "and this thing must not break apart for foolish reasons."
Three weeks later, Dorothy Hunt was dead.
If Nixon knew of a plot to kill Dorothy Hunt, he did a good job hiding it on his secret White House tapes. The day after the crash, Nixon took a call from Colson at Camp David, which was recorded by a phone in the study that automatically activated when Nixon was in residence.
"I just got a terribly tragic bit of news," Colson announced three minutes into the conversation. "That plane crash - Howard Hunt's wife was on it." Nixon interjected with real surprise in his voice, "His wife is dead?" Colson responded, "Yes sir, she was killed in that plane crash in Chicago."
Nixon was thunderstruck. "Oh my God!" he exclaimed.
Colson called it a "tragedy" and wondered how Howard Hunt would "survive it, with what he's gone through." Colson knew Dorothy Hunt well, as the families socialized after Hunt and Colson met at alumni events for Brown University graduates in the Washington area. "She was an extraordinary woman, just extraordinary," Colson told the president, adding, "a rare, gifted woman, a multilinguist, brilliant, a lot of charm."
And maybe more than that: According to Howard Hunt's 2007 autobiography, Dorothy acted as a source and asset for the CIA.
On Monday, Dec. 11, Nixon huddled with his chief of staff, H.R. Haldeman, and raised the question of the traceability of the $10,000 found in Dorothy's purse. Howard Hunt had claimed Dorothy was taking cash to a cousin in Chicago to invest in Howard Johnson hotels, and Haldeman said the story was probably true. "They have a pattern of dealing in cash," Haldeman said of the Hunts.
Fifty years later, it is still unclear whether there was "foul play," as the National Transportation Safety Board characterized the speculation, in the downing of United 553. The NTSB ruled the crash an accident due to pilot error. The Cook County coroner's office, which initially described one of the first-class passenger fatalities as resulting from "apparently some explosive force" and another in the coach section as "blast injuries and severe burns," later confessed to "a bad choice of adjectives" and clarified that the victims died of "injuries from high energy impact."
What's clear, though, is the influence the crash had on the arc of the Watergate scandal. It was a crucial turning point. Howard Hunt, worried his children would be orphans if he spent years in prison, asked his lawyer to meet with Colson and request a pardon from Nixon after a year of incarceration if Hunt would plead guilty and avoid trial.
Colson spoke with Nixon, as recorded in White House tapes. Nixon agreed to the clemency proposal.
Four other Watergate defendants, Cuban Americans from Miami whom Howard Hunt had brought to the burglary operation, took this as a cue that they'd be pardoned, too, and also pleaded guilty.
Later, when Hunt was facing sentencing, he blackmailed the White House, threatening to disclose "seamy things" about other work for Nixon's team unless he received more money to pay his legal fees and cover his family's living expenses for at least a year until his sentence was commuted, as he expected.
It didn't work out that way. Watergate continued to snowball, and Nixon was forced to resign in August 1974. Howard Hunt spent 33 months in prison. He was never pardoned for his crimes.
James D. Robenalt is the author of four nonfiction books, including "January 1973: Watergate, Roe v. Wade, Vietnam, and the Month That Changed America Forever."