Section 20 sets up shop in Budapest, where the apprehension of an ex-IRA gunrunner leads to a shocking discovery: a planned al-Zuhari attack on an upcoming holy day. Fighting the clock, the team looks to thwart a weapons heist orchestrated by MacKenna at a railway depot, but is undermined by Stonebridge's inability to focus at a critical moment. Meanwhile, Scott is rattled by a Dalton revelation.