In just a month, America will observe the tenth anniversary of the 9/11 terrorist attacks.
Over the past decade, the U.S. government has relentlessly pursued the al Qaeda masterminds behind that day's catastrophic events: Osama bin Laden has been killed, Khalid Sheikh Mohammed has been captured and Ayman al Zawahiri remains on the run.
But a new federal lawsuit claims that the tentacles behind the deadliest terror attack in American history stretch even further than al Qaeda--all the way to Tehran.
The suit was recently filed in a Manhattan court on behalf of the families of 9/11 victims. It accuses the Iranian government of having advance knowledge of the attacks and helping to facilitate travel for the 9/11 hijackers.
Three Iranian defectors from inside Iran's spy services are the key witnesses in the case.
The suit identifies the man at the center of this al Qaeda-Iran nexus as Imad Mugniyeh, a terrorist mastermind with a long history of directing attacks against U.S. interests.
Mugniyeh worked with both Iran and Hezbollah before being killed by a car bomb in 2008.
"You have travel from Beirut with Imad Mugniyah, travel into Iran with Imad Mugniyah, who apparently now, the defectors have told us, was actually in the meetings planning 9-11," said Janice Kephart, national security policy director for the Center for Immigration Studies.
Kephart worked on the bipartisan 9/11 Commission, whose report examined Iran and Hezbollah's relationship with the 9/11 hijackers.
"Detainees have described the willingness of Iranian officials to facilitate the travel of al Qaeda members through Iran, on their way to and from Afghanistan," the commission said in their report.
"For example, Iranian border inspectors would be told not to place telltale stamps in the passports of these travelers," the commission noted. "We now have evidence suggesting that eight to 10 of the 14 Saudi "muscle" operatives traveled into or out of Iran between October 2000 and February 2001."
According to Kephart, "That was a policy by the Iranian government to let al Qaeda through. The border officials were told to let al Qaeda through."
One former CIA operative who worked on this 9/11 lawsuit told CBN News that Iran's ongoing war against America dates back to 1979, when it seized the U.S. Embassy in Tehran.
"Repeatedly since then, Iran has mounted attacks against U.S. civilians and the military, and many Americans have died," former CIA operative Clare Lopez said.
"To this day, Iran continues to provide material and direct support to militias in Iraq and to the Taliban, which are killing American troops in those areas of operation every single day," she told CBN News.
The 9/11 Commission's report recommended that the U.S. government should further investigate Iran's possible involvement in the planning of 9/11. That has not happened.
"The Obama administration...has decided to take a more lenient, more kid glove approach with Iran," Kephart said.
So it appears it's up to the 9/11 families to hold Iran accountable.