'NCIS' Crossover Sneak Peek: Alden Parker Meets the 'NCIS: Hawaii' Team (Exclusive)

The three-hour crossover event airs Monday.

It's a big NCIS team-up!

The three-hour crossover event kicks off Monday night with NCIS, followed by NCIS: Hawaii and NCIS: LA, and only ET exclusively premieres a sneak peek from the second hour from Hawaii.

In the clip, NCIS' Alden Parker (Gary Cole) meets members of the Hawaii team as they go over the big case that's brought all three teams together. As the scene plays out, it's clear Parker isn't used to the dynamics of the team.

This is the first time all three NCIS teams, led by Vanessa LacheyLL Cool JChris O'DonnellSean Murray and Wilmer Valderrama, will participate in one storyline on the same night.

The NCIS crossover will center around a very personal, high-stakes case to take down a mysterious hitman.

According to CBS, team members from the different NCIS divisions come together in Washington, D.C., to celebrate a beloved FLETC (Federal Law Enforcement Training Center) professor who taught multiple members of each of the squads. On the eve of the celebration, the professor is found dead of an apparent suicide and his former students immediately suspect foul play. While investigating his past, they uncover a mysterious hitman and the more they dig into it, the bigger the targets on their backs become. Members of the team are suddenly kidnapped and all the agents must come together to take down the assassin and save their own.

The NCIS crossover kicks off Monday at 8 p.m. ET/PT on CBS, followed by NCIS: Hawaii and NCIS: LA.