Season 4

The crew of HMAS Hammersley uncovers a terrorist plot to assassinate a senior US official. Kate has doubts about Hammersley's popular new crewmate, a war hero with a dark secret. Mike resists a promotion to Navcom, even though it would allow him and Kate to pursue their relationship.

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 protected waters in the Arafura Sea, a lazy comment from one Hammersley crew member to another that it's "about as routine as its gets" is the ironic curtain raiser to a day of horror. The crew of Hammersley launches a daring raid to recover a cargo of stolen uranium from armed terrorists. Kate queries Dutchy's professionalism after he injures her during a boarding party, and Mike's godson is taken hostage by smugglers.

A series of shocking surprises await the crew when they discover a secret community living on a tropical island. Robert risks his life to save Bomber during a gunfight with drug runners, and Mike investigates claims of an illicit romance between two crew members.

Dutchy and Charge take drastic action to catch two prison escapees on a remote island. Hammersley rescues a kidnapped pilot with a dangerous secret. Charge finds himself in a psychological battle with a convicted murderer and Bird gets more than she bargained for when a routine operation turns nasty.

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.

The sinister business of organ harvesting sees two of the Hammersley's favourite sailors facing their own mortality.

There is something strange about the suspected foreign fishing vessel that a crew from Hammersley boards in the Timor Sea. On the deck are four Australian men who claim to be on a fishing trip, but Dutchy is suspicious of a fishing boat that seems to be carrying no bait, no nets, no fish and without any "blood and guts" on the deck. Further investigation reveals a cargo of illicit alcohol — and results in the XO being held hostage with a machete at her throat while the rest of her crew is sent packing.

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.

When 2Dads goes missing on a scuba diving trip, Charge risks his life and career to find him. Mike creates a diplomatic incident when he searches a North Korean ship suspected of smuggling.

Hammersley is caught in a war zone while delivering aid to a remote foreign island. Swain and Dutch risk their lives to rescue an aid worker and her sick patient from a deadly tribal feud. Mike faces a deadly dilemma when Bird is struck by a mystery illness and requires urgent evacuation.

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.

Bomber faces disciplinary action after a violent confrontation with illegal fishermen. Kate is blinded by a deadly toxin, sparking a desperate race to find an antidote, and 2Dads' plan to help Bomber gain a promotion backfires when they are kidnapped.

Mike is tortured and faces death when he is captured by a ruthless gang of drug traffickers. Dutchy and the crew vow revenge when one of their mates is presumed murdered. After realising she has no romantic future with Mike, Kate makes a fateful decision about her career.