Someone's been pranking the NCIS gang, just as the writers of the series have been teasing us with possible replacements for Ziva.
NCIS Season 11 Episode 6 centered on an explosion at an oil rig, which necessitated the involvement of CGIS Special Agent Abby Borin, as well as SecNav Sarah Porter, the latter of whom was sent to oversee the investigation, just in case it turned out to be a matter of national security. (Read: terrorists).
Turns out it was just another get-rich-quick scheme by a lawyer for the oil company, who decided to short-sell his stock in the firm right before he smuggled a bomb onto the rig. He netted tens of millions of dollars out of the deal.