In the secretive world of US/Australian Joint Defense Facility Pine Gap, the A-Crew intelligence team is faced with a terrorist attack on a civilian plane and the stunning discovery that there is a mole in their midst.

Following his demotion, Gus and Jasmina investigate who really shot down Flight BM-24 while Ethan and Kath narrow their malware suspects to somebody within A-Crew.

Kath, Ethan and Rudi discover each of the malware suspects has ample motives, and the unpredictable US President orders a US warship to undertake a provocative voyage through the South China Sea.

Jacob threatens Jasmina after witnessing her crossing the line, forcing her to confess to Gus. Meanwhile, Moses's new discovery has the potential to cause significant consequences.

As tensions in the South China Sea remain at breaking point, Gus and Jasmina's relationship stumbles and the US prepares to launch an air strike on a Chinese-claimed island.

In a race against China, A-Crew desperately scour the South China Sea for signs of the missing US pilot while the net closes in on the Pine Gap mole.