The reason why Cassidy's team had the weekend duty, not Gibbs' as it originally was intended to be, is explained by Weatherly to be because Gibbs wanted to spend some quality time with Hollis Mann instead, as shown in the start of the episode. Together with the focus on dead NCIS agents, the thought about being the one themselves is another big part of the episode. Especially McGee and DiNozzo talks about it, leading up to the death of agent Cassidy at the end of the episode.