Keep an eye on Abby and Gibbs. As season seven moves along, these two will grow closer.
A marine is found dead on the night before Halloween. Gibbs and the team investigate on "Code of Conduct."
Halloween is no laughing matter on the episode "Code of Conduct." A marine turns up dead, following a practical joke.

NCIS Season 7 Episode 5 Quotes

Gibbs: No costume this year?
Abby: After last year's Jonas Brothers debacle, Vance banned costumes. McGee? Skinny jeans? Didn't work.

Ducky: Interesting date for such a ghoulish demise.
Palmer: Yeah, it's a really cool way to go! [silence] Cool, as in the temperature. Liquid nitrogen. Forget it.