Mac and Jack pursue a lead on Nikki but it's a set up. She left something for Mac which he needs to figure out what it is. But before he could Thornton sends them to Germany. It seems like a woman is going to testify against her employer who is selling weapons to enemies of the US. She received an email from an agent telling her to meet him by train. But Thornton says the agent was killed before the email was sent. So her employer is setting her up. So they get on the train and find her. But there's a team of assassins who are out to kill her. But when the team stops them, they decide to just destroy the train by disabling it causing it to crash. So Mac needs to find a way to save everyone on the train.