The FBI agent who began the investigation that led to David Petraeus' resignation is a veteran counterterrorism expert who helped foil a millennium terror plot in Los Angeles.
Frederick Humphries, 47, was the agent who initially saw the emails that Gen Petraeus' biographer, Paula Broadwell, sent to Tampa socialite Jill Kelley.
Ms Broadwell apparently saw Mrs Kelley as a rival for the former CIA director's affections.
But Agent Humphries thought the emails raised more serious concerns because they detailed the comings and goings of Gen Petraeus and General John Allen, the top US commander in Afghanistan.
The first anonymous email warning Gen Allen to stay away from Mrs Kelley was sent in May, under the pseudonym "Kelleypatrol."
Gen Allen forwarded it to Mrs Kelley, who then got in touch with her FBI acquaintance.
Agent Humphries - who played a key role in stopping a terrorist attack aimed at blowing up Los Angeles International Airport just as the year 2000 dawned - has now found his own conduct under review.
The FBI is reviewing a telephone call he made in late October to Republican Congressman Dave Reichert to voice concern that the bureau was not aggressively pursuing a possible national security breach.
Lawrence Berger, the general counsel for the Federal Law Enforcement Officers Association, said Humphries did nothing wrong.
"He's committed no misconduct," Mr Berger said and predicted he would be cleared of any allegation.
Questions were also raised about the fact that, sometime before this investigation, Agent Humphries had sent jokey photos of himself shirtless to Mrs Kelley.
Over the summer, he was warned by his superiors to steer clear of the developing case because they had concerns he had become too personally involved.
Meanwhile, the backlash for the two women caught up in the scandal continues.
Mrs Kelley's pass to enter MacDill Air Force Base in Florida, where she met the two senior generals, has been indefinitely suspended.
Paula Broadwell's security clearance has also been revoked. As a former army intelligence officer, she had high security clearance.
Officials who have seen the communications between Gen Allen and Jill Kelley described some of the emails as "suggestive".
They said their release would be embarrassing.
Gen Allen has been allowed to keep his job as US commander of the Afghan war for the time being.
But his nomination to become the next commander of US European Command as well as the Nato supreme allied commander in Europe is now on hold.
Defence Secretary Leon Panetta has said "No one should leap to any conclusions" about him.