Blood related or not, Abby and her brother, Luca, share a strong bond. It's a bond that has the NCIS lab tech convinced her brother is still alive even when Gibbs tells her the plane he was on crashed.

The "NCIS" and "NCIS: New Orleans" teams join forces to investigate the lethal poisoning of the plane's passengers and Luca's possible involvement in the two-part crossover event tonight on CBS.

After Agent Pride (Scott Bakula) informs Gibbs (Mark Harmon) that Luca's (Lev Gorn) name was on the flight manifest, Gibbs takes Abby (Pauley Perrette) down to her lab to break the bad news. She refuses to believe Luca's dead or that he would even get on a plane in the first place.

In part two of the crossover, Bishop (Emily Wickersham) drives all night from D.C. to New Orleans in an unmarked van to deliver a body to Loretta (CCH Pounder) at the coroner's office. Elsewhere, Ducky (David McCallum) and Palmer (Brian Dietzen) act as a decoy in the NCIS van to distract a gang of Russians looking for the same body.

The crossover episode starts with "NCIS" at 8 p.m. followed by "NCIS: New Orleans" at 9 p.m. on CBS.