The NCIS team searches for answers when the current husband of both Gibbs's and Fornell's ex-wife is suspiciously kidnapped.

Gibbs teams up with FBI Agent Fornell on a joint NCIS/FBI investigation after Fornell becomes the target of a shooting, but they face an unexpected twist in the case when their mutual ex-wife, Diane Sterling, gets involved. Meanwhile, rumors run wild among the group after Diane stays overnight at McGee’s.

Complications arise when the NCIS team discovers a link between a murder victim and the current boyfriend of Gibbs and Agent Fornell’s ex-wife. Meanwhile, NSA Analyst Ellie Bishop adjusts to joining the NCIS team.

The NCIS team investigates copy-cat crime scenes while Gibbs navigates two ex-wives relentlessly trying to get his attention.

Former FBI Agent Tobias Fornell pleads with Gibbs to do whatever is necessary to take down drug dealers and suppliers in the area after his daughter, Emily Fornell, is hospitalized from an opiate overdose. Gibbs is haunted by the personal aspects of the case and his history with vigilante justice.