Donald Mallard: It's a microscopic dart.
Leroy Jethro Gibbs: Where'd it come from?
Donald Mallard: I extracted it from Corporal Beck's arm here. This contusion alerted me to the injection site. The dart is designed to be left behind, beneath the dermis. It's so small, sharp, and thin that it would've felt like... well, nothing more than a bug bite.
Abby Sciuto: [entering] Botulinum toxin.
Leroy Jethro Gibbs: What?
Abby Sciuto: He didn't ask yet?
Donald Mallard: Mere seconds away.
Abby Sciuto: My timing is off today.
Leroy Jethro Gibbs: Abs, what was in the dart?
Abby Sciuto: Now is when I'm supposed to swoosh in and say...
Donald Mallard: Botulinum toxin. The most poisonous natural substance known to man.