▶ Watch Video: Secret concert held for children of fallen heroes

Each year, intelligence professionals, special operators and the children of fallen heroes gather for a heartfelt cause — with no written invitations and a time and place so secret, it’s on a need-to-know basis.

A professional keeper of secrets, retired CIA officer Mark Kelton now sits on the board of an event so cloak and dagger, even the name is shrouded in secrecy.

“We like to call it a ‘covert concert event,'” he told CBS News’ Catherine Herridge. “We come from a secret world, it’s on a need-to-know basis, and that adds somewhat to the mystique of the event.”

Some past performers are far from unknown – ZZ Top, The Steve Miller Band and Peter Frampton. One year, Lenny Kravitz rubbed shoulders with a four-star general. 

To date, more than $3.5 million in scholarships has been raised for the CIA, Special Operations and Defense Intelligence memorial foundations. 

“These scholarship made it possible for me to go through school,” said Alison Spann, this year’s concert emcee and a scholarship recipient, who is now a local TV journalist. Her CIA-officer father, Mike Spann, was the first American killed in Afghanistan after 9/11.

“Every day is Memorial Day for my family,” Spann told CBS News. “We think about my dad all the time. He really believed in the United States and he believed that this was the best country in the world.”

One of the last videos taken of Mike Spann was of him interrogating John Walker Lindh, who was later branded the “American Taliban.” Alison, whose father died in 2001, described how the classified nature of her father’s work made the grieving process more difficult.

“There are so many questions that are left unanswered, and I think that that part’s hard,” she said. “And the truth is, we will probably never know exactly what happened there.”

Every year as more stars are added to the CIA Memorial Wall, the covert concert brings together the children of the fallen heroes to build new friendships and support their futures.

Maybe someday the event will be declassified, or it will leak — “but not on my watch,” said Kelton.