After opening the series with back-to-back losses, the Ferns needed to pull out something special to keep series alive. Instead they pulled out their worst attacking performance of the season, committing more than 40 turnovers in a muddled and error-ridden display which saw them go down 55-43.
The bright patch for the Ferns a 15-8 third quarter win, which saw them claw back a 30-19 halftime deficit to 38-34 heading into the final turn.
But all that hard work was quickly undone in the final period, as the wobbles set in again and in the blink of an eye the Diamonds, who made a series of key changes at the break, were back out to a lead of double-figures.
A clearly frustrated Silver Ferns skipper Katrina Grant admitted it was not good enough.
"I feel like that third quarter was where we had the game, and then Aussie came out and put the foot down," she said.
"I was happy with our efforts in defence - we had more turnovers in the first half than we had in the other two games combined, but then we just threw it straight away."
They didn't just throw it away. They stepped. They gave away offensive penalties. They broke on the centre pass. They missed shots.
In the end the 12-goal scoreline probably flattered the Ferns, who at times were made to look ordinary by what was a young, new-look Diamonds line-up.
The New Zealand side are now staring down the barrel of a whitewash if they can't get their act together before Saturday's finale in Sydney.
The Diamonds are also eyeing improvement in the final test, with skipper Caitlin Bassett singling out her side's third quarter slump as a key work-on for the weekend.
"The game kind of had ebbs and flows. We had a good lead and then we squandered it, so that is something we really need to look at before the next one," said Bassett, who was benched in the final quarter after being restricted to just six goals in the third spell.
The Diamonds dominance in this series is a major turnaround from last month, when the Silver Ferns pulled off a shock 57-47 win in the Quad Series decider in Invercargill, to claim their first series win over the Australians since 2012.
They were desperate to get their hands on more silverware in this series, but that desperation has not translated into results.