In the aftermath of the previous episode, the NCIS team continue to find associates of the international terrorist group, the Calling with the team discovering that the Calling are not only recruiting young children and teenagers through the Internet but that the group itself is also purchasing S-bombs off the black market. As such, the case turns into a global effort, bringing NCIS into contact with various federal agencies all over the world while NCIS itself later suffers a huge tragedy when one of their own is killed in a blast while Gibbs, having been left haunted by his failure to help Bradley Simek attempts to help Luke Harris, a young, vulnerable teenager from falling victim to the Calling.