A  man falls onto a spiked fence during a costumed tour of The Rocks.

NCIS: Sydney gets called in because he's Petty Officer First Class Eddie Baker.

Rosie notes that the impalement likely didn't kill him as there's a gunshot wound just above his heart.

There's signs of a scuffle in a room up above.

Blue says that prints on the recovered shell casing belong to Frank Doherty, a sailor who jumped ship in Sydney in 1971.

J.D. finds a Navy Cross in the desk drawer of Baker's office.

He and Mackey visit the Royal Austalian Navy Heritage Center, where they learn Baker has visited there several times to authenticate old medals.

Checking a microfiche number Baker had, they discover Doherty had won that Navy Cross.

Their theory is that Baker was trading old medals.

Blue and D track down Doherty's girlfriend at the time of his disappearance, May.

Evie and D capture Doherty at May's home.

Doherty claims Baker was blackmailing him and May and that's why Doherty killed him.

Blue says gunshot residue tests on Doherty's hands came back negative.

Mackey and J.D. disagree over whether Doherty killed Baker.

Rosie determines the pub where Baker ate his last meal.

The Rocks tour operator saw Baker and Doherty dining together on the night Baker died. He also witnessed Doherty and another man enter the building from which Baker fell.

Baker was returning medals to their rightful owners.

May says Doherty had become a father figure to Baker, who had lost his father to war. Doherty never told her who was extorting him.

Doherty is protecting his extortionist so he won't hurt May.

Mackey turns off the mike in interrogation as she tells Doherty about the mission that still haunts her.

Doherty admits Baker got shot because he got into a struggle between Doherty and the extortionist. But he still refuses to give up that name.

D wants to find a loophole for Doherty.

Doherty informs Mackey that he threw out his medal but May fished it out of the trash and bequeathed it to the Navy Heritage Museum.

Standish, the museum curator, is the extortionist and Baker's killer.

Standish is running and he's extorting one last big payment out of May.

They find May holding a gun on Standish but they convince her to put down the gun when D explains how she can keep Doherty in Australia.

Doherty and May are wed by the tour operator, with the team in attendance.