Ziva surprises Gibbs with a cryptic warning, prompting him to question why she remained underground for years while being presumed dead by family and friends, and what led to her return.

Gibbs and the team help Ziva with the "one thing" she said she'd take care of before returning to her family.

While pursuing a dangerous arms dealer, the team is shocked when Bishop is implicated in an old NSA leak while Gibbs and Marcie realize the killer they've been tracking may be onto them.