Alex is sent on a mission for Scorpia to prove his loyalty, with Tom and Kyra following close behind hoping to rescue him. Meanwhile, the Department attempts to unlock the secret of 'Invisible Sword'.

Cast: Otto Farrant, Stephen Dillane, Vicky McClure, Brenock O'Connor, Ronkẹ Adékoluẹjo, Marli Siu, Thomas Levin, Jason Wong, Sofia Helin, Kevin McNally, Eline Powell, Shelley Conn