Leading by 10 points after almost 22 minutes in the final term, South Mandurah would have thought it was home but two late goals from Halls Head snatched victory.
The Falcons led by as much as 16 points during the second term but a resilient Halls Head, spearheaded by forward Dean Buszan, were able to reel them in.
Joshua Gorman, Travis Justins and Phillip Walshaw were among the best for Halls Head, while Rhys Price was in fine form for the Falcons.
South Mandurah starts its season 0-2 after last week’s loss to Waroona.
The Tigers continued on their merry way, claiming a clinical 32-point win over Rockingham at Anniversary Park, 15.8 (98) to 10.6 (66).
Pinjarra led comfortably at every change, with Riese Wilkey booting three goals while Dominic Martin, Stephen Martin and Mitch Brown grabbed two each.
Aaron Fury and former Peel Thunder player Brennan Gillam were also impressive for the Tigers.
Kyle Hinchcliffe was a highlight for the struggling Rams side, booting five, while skipper Rocky Collins was also solid.
In Mundijong, the Centrals held off a brave Mustangs outfit to win 12.11 (83) to 10.11 (71).
Devin McFarlane and Michael Grainger were among the best for Mandurah, while Callum Marshal was impressive for the hosts.
Waroona will be rueing its 13.10 (88) to 8.8 (56) loss to the Brumbies after leading at every change before being blown away in the last term.
The Demons led by a point at three quarter time but struggled to contain Baldivis in a six goal to one final term.
David Tawhai and ex-Peel Thunder star Eddie Dann were influential for Baldivis, while Josh Commisso and Matt Thomas were among Waroona’s best.
Next week Mandurah will welcome Waroona, Halls Head will host Rockingham and South Mandurah host Pinjarra, with Centrals versus Baldivis rounding out round three.