Special Agent Bass has his target in his sights but he's on another continent. If he wants him to talk he'll need a clever plan – and maybe a bit of luck.

The team persuades The Gas Man to step out from the shadows. He reveals the first big clue in the investigation to how he got away with it – and makes a surprising claim about his role in the case.

Chloe makes a startling discovery about another chemical trafficker that has consequences for her investigation. A Kurdish survivor of mustard gas shares her story