In addition, Mason Snr was once a member of an eight men that a previous President of the United States (assumed to be Ronald Reagan due to the burial location he gives) had created so that the team themselves could travel the world and enforce justice and law, all without reporting to the chain of command. Mason Snr was given the position of team leader and trained the other seven operatives.
After the training, Mason and the team went on several black ops around the world but the program was cancelled in the early 1990s as there was only three surviving members of the original team. The remaining three had their own backgrounds changed and upon returning to civilian life, were told to never ever make contact with each other for the rest of their lives.
However, in late September 2010, Walter Carmichael killed the third surviving member of the team before abducting Mason's granddaughter. Medical Examiner Dr. Donald Mallard determined that Carmichael was doing this out of the fact that he felt guilt for the crimes that he and his team had committed in the past and as such, Carmichael felt that the wrongdoings were being set right which he knew could be only achieved by finding and also killing his former teammates.
Mason Snr went off the grid and attempted to save Rebecca but the NCIS Major Case Response Team led by NCIS Special Agent Leroy Jethro Gibbs later arrested Mason Snr despite Mason Snr putting up a brave fight against NCIS Special Agents Ziva David and Timothy McGee.
With Mason Snr the last on Carmichael's list, Carmichael decided to trade his former team leader in exchange for Mason Snr's granddaughter but during the exchange, Mason Snr broke free, causing Ziva to shoot him.
Satisfied that Mason Snr was dead, Camichael then told them that she was in the boot of his car at which point Mason got up, revealing that all had been a sting with Ziva firing blanks and Gibbs faking an argument with her over the shooting to make it sound coherent.
After that, Mason and his son along with his son's wife had an emotional reunion with their daughter while Carmichael was previously arrested and jailed for his own crimes.