Monica Lewinsky's arrival at the federal courthouse here to testify to the grand jury marks the closing phase of an investigation which has gripped the US and much of the world over the past eight months. But how did this 25year-old woman find herself in a position where the fate of a President may depend on her words?
The story began in June 1995 when she came to Washington from California as a 21-year-old White House unpaid intern. By the end of the year she had got a permanent job but she had also begun a relationship with President Clinton as she sought excuses to bring him documents in the Oval Office.
By April 1996, aides to the President were alerted to "imprudent" behaviour by Ms Lewinsky and she was discreetly moved to a job in the press office of the Pentagon across the Potomac from the White House. There she met Linda Tripp who had also moved from the White House and to whom she confided details of her relationship with the President.
Ms Tripp was in the bad books of the White House for an interview she gave to Newsweek over an incident between President Clinton and Kathleen Willey, a former aide to whom he allegedly made a sexual advance.
Then both Ms Lewinsky and Ms Tripp received notice that they would have to testify in the civil action brought by Ms Paula Jones against Mr Clinton for alleged sexual harrassment while he was governor of Arkansas. Ms Jones's lawyers had heard rumours of Ms Lewinsky's claims of a sexual relationship with the President. Ms Tripp began secretly taping conversations with Ms Lewinsky. Ms Tripp says she did this for her own protection as the younger woman was urging her not to tell the truth in her testimony.
By the beginning of this year, events were moving very fast. On January 12th, Ms Tripp handed her tapes of the conversations over to the Independent Counsel, Kenneth Starr. Until then he had been investigating the role of President and Mrs Clinton in a failed property development called Whitewater in Arkansas in the 1970s and in some other controversies in the White House such as illicit use of FBI files and the dismissal of the travel office staff.
Ms Tripp was then asked to wear a hidden microphone for the FBI and record Ms Lewinsky's answers to specific questions about her relationship with the President and whether he asked her to lie about it under oath.
Three days later, the prosecutors confronted an astounded Ms Lewinsky with the information on the tapes and demanded her co-operation on threat of possible indictment for perjury. After talking to her mother and family lawyer she refused.
But she had also been discussing her situation over the subpoena in the Paula Jones case with the President, whom she met in the White House on December 28th. He may have suggested ways their relationship could be concealed such as the disposal of presents he had given her.
Ms Lewinsky soon afterwards gave sworn written testimony to the Paula Jones lawyers that she never had sexual relations with the President and denied he asked her to lie about this.
There may also have been discussions of getting her a job away from Washington. A confidant of the President, Vernon Jordan, obliged by getting her a post with Revlon, of which he is a director.
By now Mr Starr was hot on the trail. He believed there were grounds for him to investigate whether the President had tried to get Ms Lewinsky to commit perjury and whether the job assistance was also part of an obstruction of justice.
The Attorney General, Ms Janet Reno, examined his information and allowed Mr Starr to widen his Whitewater investigation into the subornation of perjury and obstruction of justice charges.
Then on January 17th, President Clinton gave his testimony to the Paula Jones lawyers in which he swore that he did not have sexual relations with Ms Lewinsky and had not tried to get her to commit perjury.
On January 21st, the first sensational news stories appeared that Mr Starr was investigating the President over his relationship with Ms Lewinsky. Four days later Mr Clinton gave the first of four public denials that he had had sex with Ms Lewinsky. He promised more information "sooner rather than later" but on the advice of his lawyers has kept silence since then.
Mr Starr began interviewing scores of witnesses before a grand jury to build up a case for possible impeachment of the President, not for having had an alleged affair with Ms Lewinsky which would not be a breach of any law, but for possible perjury by himself and subornation of perjury.
For six months, Mr Clinton refused invitations from Mr Starr to testify voluntarily to the grand jury. Two weeks ago he was served a subpoena and has now agreed to testify on August 17th.
For six months, Ms Lewinsky refused through her lawyer, Mr Ginsburg, to testify unless she got full immunity. Mr Starr was unwilling to give her this until he interviewed her. She was in increasing danger of indictment for perjury.
Then she changed her Los Angeles malpractice lawyer for two experienced Washington lawyers and a deal was struck - full immunity for her testimony.