Tragedy rocks HMAS Hammersley as the crew races to prevent a terrorist attack on a busy Australian port. Meanwhile, Kate and Dutchy discover ingredients for a radioactive 'dirty bomb' are being smuggled into Australia on illegal fishing boats, and Mike is stunned to realise SAS Officer Jim Roth has proposed to Kate - will he let the woman he loves marry another man?
2Dads and Charge come under fire while investigating a UFO sighting. Ryan and Bird befriend a young man with a tortured secret that could get them all killed. Charge hides a health scare that could end his navy career, and Mike suspects a local police chief of masterminding a major drug-smuggling operation.
As part of the boarding party checking a possible FFV, Dutchy doesn't hide his surprise at seeing one of the crew is SAS Captain Jim Roth. His flash of recognition is noticed by the ship's master, and the question now is, has Jim's cover been blown? ASIO "spook" Madelaine Cruise is furious. She confirms that Jim was on a mission and insists CO Mike Flynn shadow the vessel in case Jim needs assistance. And so he does, after Dutchy sees two men fighting on the deck, and the subsequent boarding party finds an area awash with blood and Jim under a tarpaulin with a serious head wound.
A suicide bomb attack in a nightclub has a shocking impact on the crew of HMAS Hammersley. Dutchy goes undercover with the SAS to capture a group of deadly extremists before they can attack Australian targets. 2Dads risks his life to save Hammersley from a bomb attack. Kate's world is rocked when her former lover, SAS officer Jim Roth, returns to Hammersley. Mike risks his career by refusing to co-operate with a high ranking ASIO spy.