The Hammersley attempts the daring capture of an illegal fishing ‘mother ship’ but is thwarted by violent eco-terrorists. Mike finds himself falling in love with beautiful marine biologist Ursula Morrell, who later goes missing under mysterious circumstances.

A new Commanding Officer and the discovery of a cruel and lucrative trade in crocodile skins results in some tense and disturbing moments for the crew of the HMAS Hammersley.

On patrol in the Arafura Sea, the Hammersley encounters an old adversary, an illegal foreign fishing vessel skippered by an infamous fisherman known as Hannibal. Robert is lost overboard in mysterious circumstances, sparking a major search and lives are at stake when Swain discovers rabies on board Hammersley.

Hammersley hunts down cattle rustlers behind the hijacking of live cattle shipments. Robert takes desperate measures to be seen as a team player by his crewmates, and Bird is terrorised by her ex-boyfriend.

The 'crash posting' of a Communications Technician to HMAS Hammersley proves to be a particularly nice surprise for one of her crew. However, 2Dads' suspicion of his old mate soon begins to grow, particularly when he suspects that Fraser is feeding vital intelligence to a group of pirates who have been ransacking boats. Mike and Kate use unorthodox tactics to catch the gang of daring pirates, .and Charge gets more than he bargained for when he finds love on a dating website.

Kate is hunted down by an obsessed criminal after she kills his accomplice during a boarding. When Bird is kidnapped, the crew fears she will be murdered as payback.

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.

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?