It seems as if there was more to their professor than meets the studious eye. As his former students look into what happened, they learn something shocking about his past. When they stumble upon a hitman and become targets themselves, things get far more dangerous. Some team members are kidnapped while the rest are left to save the day.
Who are the victims and who are the heroes? Tune in for the epic NCISverse crossover event when all three series return on Monday, Jan. 2 on CBS!
Source: https://www.distractify.com/p/when-does-ncis-return