Here's what happened:
* DiNozzo's father, Ari, is killed by a mysterious group called the "Front." This group was targeting Ari because he was an undercover agent for the CIA.
* DiNozzo is framed for Ari's murder and forced to go on the run. He knows he can't clear his name because his own family is the target.
* He eventually escapes and teams up with Ziva David, the NCIS agent he has a romantic connection with. They travel to Israel to seek help from her family.
* DiNozzo's escape is made possible by the team's efforts. They gather evidence to clear his name and expose the "Front."
* Facing a dangerous future and the potential for more threats, DiNozzo chooses to enter Witness Protection.
* The finale ends with DiNozzo saying goodbye to the team and starting a new life with a new identity.
It's important to note that DiNozzo later returned to NCIS in Season 13. His departure and return was a major plot point in the show's history.